Unit 4: Trigonometry

Minds On 

Unit 4: Trigonometry

Minds On

Angle Sin Cos Tan                    

Learning Goals:

I can use the CAST rule to determine if a Trig Ratio is positive or negative.

I can determine the value of the Reciprocal Trig Ratios using what I know about the Primary Trig Ratio.

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

The CAST Rule helps us to determine if a trig ratio will be positive or negative.

C

AS

T

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

Determine if the following are positive or negative. Do not evaluate. 

a) Sin (310º) b) Cos (17º) c) Tan (201º)

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

What is a reciprocal?

 

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

Primary Trig Ratios

Reciprocal Trig Ratios

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST RuleSince most calculators don’t have Csc, Sec, and Cot,

buttons, we can calculate them using the primary trig ratios.

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

If θ = 30º, determine the value of Csc θ.

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

If θ = 45º, determine the value of Sec θ.

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule 

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule 

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule 

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

Why does CSC = not exist?

Does an angle satisfying Sec = exist in the third quadrant? Explain.

Unit 4: Trigonometry

Lesson 3 – Reciprocal Trig Ratios and CAST Rule

Homework

Pg. 246 #5-7, #10-12