2. SINE AND COSINE AS COMPLEMENTS ~ adapted from Walch Education

3.  Examine HEY! DOES THIS RELATIONSHIP WORK FOR sin B AND cos A?

4.  In, sin A = cos B, and sin B = cos A  This relationship between sine and cosine is known as an identity Using this triangle, show that this relationship works for every right triangle

5. WHAT ELSE?!? The two acute angles in a right triangle have a sum of 90°. They are complementary angles. WWhat is the mathematical expression?

6. COFUNCTION IDENTITIES This looks like something I should remember

7. OH…THAT’S WHAT THAT MEANS The value of one ratio for one angle is the same as the value of the other ratio for the other angle.  So we can use the sine of one acute angle to find the cosine of its complementary angle (AND VICE –VERSA)

8.  Let’s try this example:  Find

9.  First step:  Second step:  Third step: Verify using a scientific calculator.  GREAT JOB

10.  See if you can figure this one out. Be ready to explain which identity you used and why:  Find a value of  for which sin  = cos 15° is true.

11. THANKS FOR WATCHING!!!!  Ms. Dambreville