SOLUTION: how to express cos(90-a) in simplest form

Algebra ->  Trigonometry-basics -> SOLUTION: how to express cos(90-a) in simplest form      Log On


   

Question 415819: how to express cos(90-a) in simplest form
Found 2 solutions by htmentor, Alan3354:
Answer by htmentor(1343) About Me  (Show Source):
You can put this solution on YOUR website!
Use the trigonometric identity cos(A-B) = cos(A)cos(B) + sin(A)sin(B).
So we have cos(90-a) = cos(90)cos(a) + sin(90)sin(a)
Since cos(90) = 0, and sin(90) = 1, this simplifies to sin(a).
Thus, cos(90-a) = sin(a)
Try an example. Let a = 90.
cos(90-90) = sin(90), cos(0) = 1 = sin(90).

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
sin(a) is simple.