Solving with Trig Identities

Question 1

What is the fundamental trigonometric identity?

Answer 1

sin²(x)+cos²(x) ≡ 1

Question 2

Once principal value is obtained, how do you get secondary values for Sin, Cos and Tan?

Answer 2

¡CHECK INTERVALS!
Sin:
180°(π if in radians) - P.V
Cos:
360°(2π if in radians) - P.V
Tan:
NO S.V!!!!

Question 3

How to solve a hidden quadratic?

Answer 3

Substitute correct formulas (e.g. sin²(x)+cos²(x) = 1) 
where needed (sub in for ² functions) and solve as a quadratic.

Question 4

When and how to change the range of the function?

Answer 4

When the input of the function is transformed the range has to be changed. (e.g. 12sin²(3x-2) )

If the range has to be changed you change the range according to the input.

e.g.
0 ≤ X ≤ 360