## Reflection: Intervention and Extension Formalizing Properties Known Informally - Section 3: Writing tangent and cotangent in terms of sine and cosine

One question that comes up a lot is why I write sec(theta) as -3/2 instead of 3/-2.

This question tells me that the students are still not proficient with fractions. To clarify I begin by asking what mathematical operation is done when you have a fraction. I then ask is -3 divided by 2 is equivalent to 3 divided by -2?

Once the students realize that both computations give the same decimal, I explain that the st standard convention is to either make the numerator negative or put the negative in front of the fraction.  I usually put the negative on top to reduce confusion about what is written. I explain that the negative in the denominator is less noticeable and that the negative on the side sometimes looks like it is just part of the notation.

When I grade work I give credit for the negative in any position of the fraction and notice that the students will move the negative to the top as the year progresses.

Common Question
Intervention and Extension: Common Question

# Formalizing Properties Known Informally

Unit 9: Trigonometric Identities
Lesson 1 of 14

## Big Idea: How can I find the value of other trigonometric functions if I only know one or two values?

Print Lesson
1 teacher likes this lesson
Standards:
Subject(s):
Math, Trigonometric Identites, Verifyting Identites
50 minutes

### Katharine Sparks

##### Similar Lessons

###### What do Triangles have to do with Circles?
Algebra II » Trigonometric Functions
Big Idea: How is the unit circle related to "triangle measurement"? A story of two equivalent definitions.
Favorites(10)
Resources(17)
Fort Collins, CO
Environment: Suburban

###### Trigonometric Identities - Day 1 of 2
12th Grade Math » Trigonometric Relationships
Big Idea: Identifying what makes a trig expression complex will keep you focused on what needs to be simplified.
Favorites(2)
Resources(14)
Troy, MI
Environment: Suburban

###### Discovering Trig Identities (Day 4 of 4)
12th Grade Math » Trigonometric Equations
Big Idea: Students use TI-Nspire calculators to develop their own understandings of what trigonometric identities are and why they work.
Favorites(0)
Resources(24)
Phoenix, AZ
Environment: Urban