# Math Help - Simple Trig Identity - help

1. ## Simple Trig Identity - help

I need help with this equation:

sin(x)cos(x)tan(x)=1-cos^2(x)

2. Originally Posted by marekd
I need help with this equation:

sin(x)cos(x)tan(x)=1-cos^2(x)
hi

some hints ,

tan x = sin x/cos x

sin^2 x + cos^2 x=1

3. Hi

substitute $\frac{sinx}{cosx}$ for tanx.

This will give you

$sinx*cosx*\frac{sinx}{cosx}= 1 - cos^2x$

as you can see the cosx will cancel on the left side of the equal sign.

This leaves you with

$sin^2x = 1 - cos^2x$

and you know the trig identity of $sin^2x + cos^2x = 1$

Does that clear everything up for you?

4. Helps a lot. Thanks you guys