Exact Value 3.

Question

Find the exact value of cos(75degrees) by using 75degrees = 30degrees + 45degrees. Please Help??!

Answer 1

Use the addition angle identity for cosine.

 

cos(30 + 45) =

 

cos(30)cos(45) - sin(30)sin(45) =

 

 

These trig terms are values on the unit circle that you should be able to easily identify.  Find them and simplify the expression.