1. Trig Identities Lesson 3
Obj – Cofunctions
- Sum & Difference Identities

2. What are cofunctions?
So, what do you notice about the functions?

3. (Functions that are equal when their Angles add up to 90 degrees.)
Cofunctions – Complementary Functions
(Functions that are equal when their
Angles add up to 90 degrees.)

5. Sum & Difference Identities

6. EX 1: Use reference triangles
to find exact values for:
A B.
C D.
E F.

9. 4
(B)

10. Ex. 5: Use your knowledge of cofunctions
or sum/difference identities to find
the value of the unknown angle
or function. A. B. C. D.

12. EX 7: Find the exact value of

13. EX 8: Find the exact value of

14. Ex. 9: Find the exact value of the Sine,
Cosine, and Tangent of the
following angle.

15. Ex. 10: For and
, find: A. B. C.

16. Ex. 11: For and
, find: A. B. C.

17. HW (Trig Identities Lesson 3 Worksheet)