Question

Verify the identity.

cos (x+(pi/2)) = -sin x

Answer 1

well use the difference of 2 angles

cos(A + B) = cos(A)cos(B) - sin(A)sin(B)

thats 1 method

Answer 2

cos (x+(pi/2)= cos x

Answer 3

oops sum not difference

Answer 4

cos=-sinx thats basically what im trying to figure out now

Answer 5

well if you make the subsitution you get

\[\cos(x + \frac{\pi}{2}) = \cos(x)\cos(\frac{\pi}{2}) - \sin(x) \sin(\frac{\pi}{2})\]

whats the value of cos(pi/2)..?

whats the value of sin(pi/2)

substitute them and seem what happens

Answer 6

wait i did the identities wrong

Answer 7

this is so confusing :(

Answer 8

an anternative is to graph the curve cos(x)

then graph cos(x + pi/2) pi/2 causes a phase shift of pi/2 to the left.... the resulting cruve... is -sin(x)

Answer 9

ok