SOLUTION: Use the addition and subtraction formulas to simplify cos(x-3pi/2). I came up with cosx for my answer. Is this correct?

Algebra ->  Trigonometry-basics -> SOLUTION: Use the addition and subtraction formulas to simplify cos(x-3pi/2). I came up with cosx for my answer. Is this correct?      Log On


   

Question 69292: Use the addition and subtraction formulas to simplify cos(x-3pi/2).
I came up with cosx for my answer. Is this correct?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Using formula:
cos%28A-B%29=cos%28A%29cos%28B%29-sin%28A%29sin%28B%29let A=x and B=3pi%2F2
cos%28x-3pi%2F2%29=cos%28x%29cos%283pi%2F2%29-sin%28x%29sin%283pi%2F2%29 Since cos%283pi%2F2%29=0 the first term is zero
cos%28x-3pi%2F2%29=0-sin%28x%29sin%283pi%2F2%29 Since sin%283pi%2F2%29=-1 the answer comes to sin(x)
cos%28x-3pi%2F2%29=-sin%28x%29%28-1%29
cos%28x-3pi%2F2%29=sin%28x%29