Is cos(x - (pi/2)) equal to cos(x)tan(x)?

[silversorrow]

cos(x-(pie/2))=cos(x)tan(x)

I have to verify this identity and can't seem to figure it out. cos (x-y)=cos x * cos y + sin x * sin y
well since cos y = 0, it kind of eliminates that side of the equation and I end up with sinx * sin1
Did I go about this all wrong?

 

[Cyosis]

It is sin(x)*1 not sin 1, because sin(pi/2)=1. So far you have cos(x-pi/2)=sin(x), which is correct. Now write out the right hand side of your original equation and see what you get.