Need help understanding trig transformations

[max]

Hi,

I was going over the cofunction identity sin(pi/2 -x) = cos(x), and I don't understand why it is true. If sin(x) moved to the right pi/2 units equals cos(x), why isn't the identity shown as sin(-x -pi/2) = cos(x)?

Thanks

 

[Mrspi]

Hi,

I was going over the cofunction identity sin(pi/2 -x) = cos(x), and I don't understand why it is true. If sin(x) moved to the right pi/2 units equals cos(x), why isn't the identity shown as sin(-x -pi/2) = cos(x)?

Thanks

You could use the "angle difference" identity:

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

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

sin(pi/2 - x) = 1*cos x + sin x* 0

sin(pi/2 - x) = cos x + 0

sin(pi/2 - x) = cos x

 

[max]

Thanks