# Trig Proof

• Oct 27th 2010, 05:19 PM
Brndo4u
Trig Proof
Could someone show me the first couple of steps of this Proof.

2/1+cosx - tan^2(x/2) = 2cosx/1+cosx.

Im working with the left side. I know to use Half-Angle I.D. I've tried all 3 tan Half angles. just keep getting hung up.
• Oct 27th 2010, 06:00 PM
skeeter
Quote:

Originally Posted by Brndo4u
Could someone show me the first couple of steps of this Proof.

2/1+cosx - tan^2(x/2) = 2cosx/1+cosx.

Im working with the left side. I know to use Half-Angle I.D. I've tried all 3 tan Half angles. just keep getting hung up.

$\displaystyle \frac{2}{1+\cos{x}} - \tan^2\left(\frac{x}{2}\right) = \frac{2\cos{x}}{1+\cos{x}}$ is not an identity.

let $\displaystyle x = \frac{\pi}{2}$ and see what happens.

fyi , the left side = 1 for all defined values of x.
• Oct 27th 2010, 06:18 PM
Brndo4u
I understand that it is not an equation. I need to verify that one side equals the other.
• Oct 27th 2010, 06:55 PM
skeeter
Quote:

Originally Posted by Brndo4u
I understand that it is not an equation. I need to verify that one side equals the other.

but one side does not equal the other ... are you trying to solve the equation for a specific value of x ?