## Spectrum Group Title tan^2 x = 1-cos2x/ 1+ cos2x true or false? one year ago one year ago

1. zordoloom Group Title

That would be true. It' an identity.

2. checkoutmymath Group Title

It's not an identity. Does tan^2x = 1-(cos2x/1)? I'm certain it doesn't. It does, however, equal to (1-cos2x)/2. This is an example of a half-angle identity.

3. Spectrum Group Title

er....er

4. Jnlucero Group Title

$\frac{ 1-\cos 2x }{ 1+\cos 2x }=\frac{ 1-(1-2\sin^2x) }{ 1+(2\cos^2x-1) }=\frac{ 2\sin^2x }{2\cos^2x }=\tan^2x$

5. Jnlucero Group Title

so its true.

6. Spectrum Group Title

um 0.0 :/

7. Jnlucero Group Title

something wrong?

8. Spectrum Group Title

you guys are confusting me 0.o true or no?

9. Jnlucero Group Title

the first i did was to use the double angle formula for sine and cosine. then it was simplified, then since the ratio of sine and cosine is tangent, then the next step is obvious.