## All posts in category **Precalculus**

# I Have a Tan

*Posted by John Quintanilla on February 9, 2018*

https://meangreenmath.com/2018/02/09/i-have-a-tan/

# Babylonian trigonometry

An interesting article that I read on Babylonian mathematics.

*Posted by John Quintanilla on February 2, 2018*

https://meangreenmath.com/2018/02/02/babylonian-trigonometry/

# Engaging students: Dividing fractions

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for *engaging* their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Kerryana Medlin. Her topic, from Pre-Algebra: dividing fractions.

**How could you as a teacher create an activity or project that involves your topic?**

One of the more practical uses of dividing fractions is cooking. Anybody who has baked in the past will know that sometimes one does not possess the proper measuring cup for the job and that they have to crunch some numbers. (This happens a lot when in college.)

The basic idea behind the activity is to ask the students to follow a recipe using a 1/3 cup measuring cup and a teaspoon. This will also allow them to practice dividing whole numbers by fractions, which strengthens to concept as well. They will be reminded that a whole number can be expressed as the number over one.

The ingredient list would be as follows:

Treats:

5-6 cups of rice cereal

1 cup of marshmallow fluff

1/3 cup of sprinkles

Buttercream:

½ cup unsalted butter

1 ½ cups powdered sugar

1 ½ teaspoons of vanilla extract

1-3 teaspoons of milk

They would be asked to figure out how many 1/3 cups each component would take. This would also help the students to use the skill of adding fractions (1 and ½ being 3/2) before dividing. The recipe would ultimately make rice cereal treats with icing on top (enough for the entire class). This is envisioned as an activity in which the students work either individually or in small groups to do the calculations and then come together as a class to provide answers and give me the proper amount of ingredients to put into the recipe.

**How does this topic extend what your students should have learned in previous courses?**

Dividing fractions involves prior knowledge from fractions, generally. If dividing by flipping the dividend and then multiplying the resulting two fractions, the student must use their knowledge of multiplication of fractions and inverses, assuming that they have learned anything about inverses at this point. If the student is taught to find the greatest common denominator first, then they will use their knowledge of greatest common denominators and basic division to find the quotient. They will also be reminded of the concept of whole numbers being expressed as fractions in this topic.

**How did people’s conception of this topic change over time? **

Originally, division of fractions would have been thought of in terms of practical use only and was likely conceptual since the symbolism of fractions was not the clearest. An example of fraction systems that were more difficult to comprehend, would be the Egyptian system, since they would add together unit fractions to represent non-unit fractions, unless it was fraction that had a repeating unit fraction, such as 2/7 = 1/7 + 1/7 (Weisstein). When symbols became clear, the division was done by taking the fractions, finding their common denominator, then dividing the numerators and denominators, leaving the quotient. The Babylonians mostly used the method of taking the inverse of the divisor and then multiplying by the dividend (O’Connor and Robertson, 2000). This is still a popular method. Today we can do either, but some believe that doing this operation algebraically might be better for students because thinking about division of fractions in only a practical sense will stifle their imagination (Ahia and Fredua-Kwarteng, 2006).

**References: **

Jamie. (2016). Birthday Marshmallow Cereal Treats*. My Baking Addiction*. Retrieved from

https://www.mybakingaddiction.com/birthday-marshmallow-cereal-treats/

Ahia, Francis and Fredua-Kwarteng, E.. (2006) Understanding Division of Fractions: An Alternative View.

Retrieved from http://files.eric.ed.gov/fulltext/ED493746.pdf

O’Connor, J. and Robertson E.. (2000). An overview of Babylonian mathematics. Retrieved from

http://www-history.mcs.st-and.ac.uk/HistTopics/Babylonian_mathematics.html

Weisstein, Eric. (n.d.). Egyptian Fraction. *MathWorld. *Retrieved from

http://mathworld.wolfram.com/EgyptianFraction.html

*Posted by John Quintanilla on November 27, 2017*

https://meangreenmath.com/2017/11/27/engaging-students-dividing-fractions-3/

# Day After Thanksgiving

*Posted by John Quintanilla on November 24, 2017*

https://meangreenmath.com/2017/11/24/day-after-thanksgiving/

# Engaging students: Ratios and rates of change

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for *engaging* their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Kelly Bui. Her topic, from Algebra: ratios and rates of change.

How could you as a teacher create an activity or project that involves your topic?

The activity I created would involve having the entire class make Rice Krispies treats as either groups or partners. The recipe I linked below calls for 6 cups of Rice Krispies, but for the sake of the activity, each table will receive 1 ½ cups of the cereal. Every table will receive the original recipe and determine how many large marshmallows they will need and how many tablespoons of butter they will need for the recipe to be modified to using only 1 ½ cups of cereal. This activity will allow students to use the ratios to convert measurements, such as 40 marshmallows / 6 cups of Rice Krispies. After a group finishes their calculations and finds the ratio of each ingredient in respect to the amount of cereal, they can begin making their Rice Krispies treats. To extend this to a project, the Rice Krispies Treats activity can be done in class and students will be assigned to find a recipe which involves either using the ratio to create a smaller or larger serving of the recipe.

How can this topic be used in your students’ future courses in mathematics or sciences?

Ratios are introduced in middle school when we compare a part to another other part or part to whole. Students also begin to grasp that 12 inches / 1 foot is a relationship between two quantities because there are 12 inches per foot. We also see the use of ratios in high school chemistry when converting units. A simple ratio we first learn is that density is the ratio of mass to volume. This can then be extended, for example, when students begin to solve for the number of moles of an element given its mass in grams. Before teaching a chemistry class that 1 mole = 6.022×10^23, instructors could begin with simple conversions of the length of a state in miles and converting that length into inches. Once students understand the process and the concept that we are taking one unit and converting it to another unit, it will be easier to apply it to more complex situations in chemistry.

As a class, to get into the process of using ratios to convert units, the students can make their own conversion ratios with different objects to model this relationship. For instance, 4 fire extinguishers are the length 1 lab table and 8 lab tables are the length 1 school bus, and based on these ratios, students must find the length of a school bus in terms of fire extinguishers. This activity will allow the students to use objects they see every day and create a relationship among them.

How has this topic appeared in pop culture (movies, TV, current music, video games, etc.)?

Shark Tank is a show which involves 5 or 6 sharks (investors) and entrepreneurs that go into the “shark tank” to pitch their ideas seeking one or more partners who will invest in their business. Most entrepreneurs seek a money amount for an amount of stake in their company or business. If the entrepreneurs are lucky, they will get a deal with one or more of the sharks. In the video below, Aaron Krause pitches his product, the “Scrub Daddy” in which he asks for a $100,000 investment for a 10% equity in his company. We see the topic of ratios appear in this business-related show because 10% equity of $100,000 means he values his company at $1 million, in other words our ratio is 10% / $100,000. This ratio can be used to find the value of the company at 100%. In addition, the sharks also like to know the breakdown of the cost per unit. In this video, Mr. Krause states that it takes $1.00 to create a scrub daddy and he sells it for $2.80 wholesale. This gives the sharks the knowledge of how much they would earn for 1 Scrub Daddy. Given the sharks are willing to negotiate, like in the video, Lori gets 20% equity of the company. For each $2.80 / 1 Scrub Daddy, she will earn $0.56.

*Posted by John Quintanilla on November 13, 2017*

https://meangreenmath.com/2017/11/13/engaging-students-ratios-and-rates-of-change-2/

# Stay Focused

From Kirk Cousins, quarterback of the Washington Redskins:

Sometimes our guests ask why I have this hanging above my desk. It’s an old high school math quiz when I didn’t study at all and got a C+… just a subtle reminder to me of the importance of preparation. If I don’t prepare I get C’s!

*Posted by John Quintanilla on August 23, 2017*

https://meangreenmath.com/2017/08/23/stay-focused/

# Pizza Hut Pi Day Challenge: Index

I’m doing something that I should have done a long time ago: collecting a series of posts into one single post. The following links comprised my series on the 2016 Pizza Hut Pi Day Challenge.

Part 1: Statement of the problem.

Part 2: Using the divisibility rules for 1, 5, 9, 10 to reduce the number of possibilities from 3,628,800 to 40,320.

Part 3: Using the divisibility rule for 2 to reduce the number of possibilities to 576.

Part 4: Using the divisibility rule for 3 to reduce the number of possibilities to 192.

Part 5: Using the divisibility rule for 4 to reduce the number of possibilities to 96.

Part 6: Using the divisibility rule for 8 to reduce the number of possibilities to 24.

Part 7: Reusing the divisibility rule for 3 to reduce the number of possibilities to 10.

Part 8: Dividing by 7 to find the answer.

*Posted by John Quintanilla on August 22, 2017*

https://meangreenmath.com/2017/08/22/pizza-hut-pi-day-challenge-index/

# Predicate Logic and Popular Culture: Index

I’m doing something that I should have done a long time ago: collecting a series of posts into one single post. The following links comprised my series on using examples from popular culture to illustrate principles of predicate logic. My experiences teaching these ideas to my discrete mathematics students led to my recent publication (John Quintanilla, “Name That Tune: Teaching Predicate Logic with Popular Culture,” *MAA Focus*, Vol. 36, No. 4, pp. 27-28, August/September 2016).

Unlike other series that I’ve made, this series didn’t have a natural chronological order. So I’ll list these by concept illustrated from popular logic.

- Part 1: “You Belong To Me,” by Taylor Swift
- Part 21: “Do You Hear What I Hear,” covered by Whitney Houston
- Part 31:
*The Godfather*(1972) - Part 45:
*The Blues Brothers (*1980) - Part 53: “What Does The Fox Say,” by Ylvis
- Part 54: “Billie Jean,” by Michael Jackson
- Part 98: “Call Me Maybe,” by Carly Rae Jepsen.

Logical or :

- Part 1:
*Shawshank Redemption*(1994)

Logical negation :

- Part 1: Richard Nixon
- Part 32: “Satisfaction!”, by the Rolling Stones
- Part 39: “We Are Never Ever Getting Back Together,” by Taylor Swift

Logical implication :

- Part 1:
*Field of Dreams*(1989), and also “Roam,” by the B-52s - Part 2: “Word Crimes,” by Weird Al Yankovic
- Part 7: “I’ll Be There For You,” by The Rembrandts (Theme Song from
*Friends*) - Part 43: “Kiss,” by Prince
- Part 50: “I’m Still A Guy,” by Brad Paisley
- Part 76: “You’re Never Fully Dressed Without A Smile,” from
*Annie*. - Part 109: “Dancing in the Dark,” by Bruce Springsteen.
- Part 122: “Keep Yourself Alive,” by Queen.

For all :

- Part 3:
*Casablanca*(1942)

- Part 4:
*A Streetcar Named Desire*(1951)

- Part 34: “California Girls,” by The Beach Boys
- Part 37: Fellowship of the Ring, by J. R. R. Tolkien
- Part 49: “Buy Me A Boat,” by Chris Janson
- Part 57: “Let It Go,” by Idina Menzel and from
*Frozen*(2013) - Part 65: “Stars and Stripes Forever,” by John Philip Sousa.
- Part 68: “Love Yourself,” by Justin Bieber.
- Part 69: “I Will Always Love You,” by Dolly Parton (covered by Whitney Houston).
- Part 74: “Faithfully,” by Journey.
- Part 79: “We’re Not Gonna Take It Anymore,” by Twisted Sister.
- Part 87: “Hungry Heart,” by Bruce Springsteen.
- Part 99: “It’s the End of the World,” by R.E.M.
- Part 100: “Hold the Line,” by Toto.
- Part 101: “Break My Stride,” by Matthew Wilder.
- Part 102: “Try Everything,” by Shakira.
- Part 108: “BO$$,” by Fifth Harmony.
- Part 113: “Sweet Caroline,” by Neil Diamond.
- Part 114: “You Know Nothing, Jon Snow,” from
*Game of Thrones*. - Part 118: “The Lazy Song,” by Bruno Mars.
- Part 120: “Cold,” by Crossfade.
- Part 123: “Always on My Mind,” by Willie Nelson.

For all and implication:

- Part 8 and Part 9: “What Makes You Beautiful,” by One Direction
- Part 13: “Safety Dance,” by Men Without Hats
- Part 16:
*The Fellowship of the Ring,*by J. R. R. Tolkien - Part 24 : “The Chipmunk Song,” by The Chipmunks
- Part 55:
*The Quiet Man*(1952) - Part 62: “All My Exes Live In Texas,” by George Strait.
- Part 70: “Wannabe,” by the Spice Girls.
- Part 72: “You Shook Me All Night Long,” by AC/DC.
- Part 81: “Ascot Gavotte,” from
*My Fair Lady* - Part 82: “Sharp Dressed Man,” by ZZ Top.
- Part 86: “I Could Have Danced All Night,” from
*My Fair Lady*. - Part 95: “Every Breath You Take,” by The Police.
- Part 96: “Only the Lonely,” by Roy Orbison.
- Part 97: “I Still Haven’t Found What I’m Looking For,” by U2.
- Part 105: “Every Rose Has Its Thorn,” by Poison.
- Part 107: “Party in the U.S.A.,” by Miley Cyrus.
- Part 112: “Winners Aren’t Losers,” by Donald J. Trump and Jimmy Kimmel.
- Part 115: “Every Time We Touch,” by Cascada.
- Part 117: “Stronger,” by Kelly Clarkson.

There exists :

- Part 10: “Unanswered Prayers,” by Garth Brooks
- Part 15: “Stand by Your Man,” by Tammy Wynette (also from
*The Blues Brothers*) - Part 36:
*Hamlet*, by William Shakespeare - Part 57: “Let It Go,” by Idina Menzel and from
*Frozen*(2013) - Part 93: “There’s No Business Like Show Business,” from
*Annie Get Your Gun*(1946). - Part 94: “Not While I’m Around,” from
*Sweeney Todd*(1979). - Part 104: “Wild Blue Yonder” (US Air Force)
- Part 106: “No One,” by Alicia Keys.
- Part 116: “Ocean Front Property,” by George Strait.

Existence and uniqueness:

- Part 14: “Girls Just Want To Have Fun,” by Cyndi Lauper
- Part 20: “All I Want for Christmas Is You,” by Mariah Carey
- Part 23: “All I Want for Christmas Is My Two Front Teeth,” covered by The Chipmunks
- Part 29: “You’re The One That I Want,” from
*Grease* - Part 30: “Only You,” by The Platters
- Part 35: “Hound Dog,” by Elvis Presley
- Part 73: “Dust In The Wind,” by Kansas.
- Part 75: “Happy Together,” by The Turtles.
- Part 77: “All She Wants To Do Is Dance,” by Don Henley.
- Part 90: “All You Need Is Love,” by The Beatles.

DeMorgan’s Laws:

- Part 5: “Never Gonna Give You Up,” by Rick Astley
- Part 28: “We’re Breaking Free,” from
*High School Musical*(2006)

Simple nested predicates:

- Part 6: “Everybody Loves Somebody Sometime,” by Dean Martin
- Part 25: “Every Valley Shall Be Exalted,” from Handel’s
*Messiah* - Part 33: “Heartache Tonight,” by The Eagles
- Part 38: “Everybody Needs Somebody To Love,” by Wilson Pickett and covered in
*The Blues Brothers*(1980) - Part 46: “Mean,” by Taylor Swift
- Part 56: “Turn! Turn! Turn!” by The Byrds
- Part 63: P. T. Barnum.
- Part 64: Abraham Lincoln.
- Part 66: “Somewhere,” from
*West Side Story*. - Part 71: “Hold On,” by Wilson Philips.
- Part 80: Liverpool FC.
- Part 84: “If You Leave,” by OMD.
- Part 103: “The Caisson Song” (US Army).
- Part 111: “Always Something There To Remind Me,” by Naked Eyes.
- Part 121: “All the Right Moves,” by OneRepublic.

Maximum or minimum of a function:

- Part 12: “For the First Time in Forever,” by Kristen Bell and Idina Menzel and from
*Frozen*(2013) - Part 19: “Tennessee Christmas,” by Amy Grant
- Part 22: “The Most Wonderful Time of the Year,” by Andy Williams
- Part 48: “I Got The Boy,” by Jana Kramer
- Part 60: “I Loved Her First,” by Heartland
- Part 92: “Anything You Can Do,” from
*Annie Get Your Gun*. - Part 119: “Uptown Girl,” by Billy Joel.

Somewhat complicated examples:

- Part 11 : “Friends in Low Places,” by Garth Brooks
- Part 27 : “There is a Castle on a Cloud,” from
*Les Miserables* - Part 41: Winston Churchill
- Part 44:
*Casablanca*(1942)

- Part 51: “Everybody Wants to Rule the World,” by Tears For Fears
- Part 58: “Fifteen,” by Taylor Swift
- Part 59: “We Are Never Ever Getting Back Together,” by Taylor Swift
- Part 61: “Style,” by Taylor Swift
- Part 67: “When I Think Of You,” by Janet Jackson.
- Part 78: “Nothing’s Gonna Stop Us Now,” by Starship.
- Part 89: “No One Is Alone,” from Into The Woods.
- Part 110: “Everybody Loves My Baby,” by Louis Armstrong.

Fairly complicated examples:

- Part 17 : Richard Nixon
- Part 47: “Homegrown,” by Zac Brown Band
- Part 52: “If Ever You’re In My Arms Again,” by Peabo Bryson
- Part 83: “Something Good,” from
*The Sound of Music*. - Part 85: “Joy To The World,” by Three Dog Night.
- Part 88: “Like A Rolling Stone,” by Bob Dylan.
- Part 91: “Into the Fire,” from
*The Scarlet Pimpernel*.

Really complicated examples:

*Posted by John Quintanilla on August 21, 2017*

https://meangreenmath.com/2017/08/21/predicate-logic-and-popular-culture-index-3/

# log(an)

*Posted by John Quintanilla on July 31, 2017*

https://meangreenmath.com/2017/07/31/logan/

# Trigonometry pun

*Posted by John Quintanilla on July 20, 2017*

https://meangreenmath.com/2017/07/20/7722/