Sunday

September 21, 2014

September 21, 2014

Posted by **anonymous** on Tuesday, May 25, 2010 at 1:02am.

1. cos^2(x/2)-sin^2(x/2)

2. 2cos^2(3A)-1

3. sin 2x/1+cos2x

I think number 3 is tan 2x?

The other two I dont know.

Thanks for the help

- MATH ANALYSIS -
**Reiny**, Tuesday, May 25, 2010 at 7:11amIt looks like you are working with the expansions of

sin 2A and cos 2A, and are expected to know those formulas

1. is a direct result of the expansion of

cos 2A = cos^2 A - sin^2 A

so cos^2(x/2)-sin^2(x/2) = cosx

2. again, direct application

2cos^2(3A)-1 = cos 6A

3. sin 2x/1+cos2x

= 2sinxcosx/(1 + cos^2 x - sin^2 x)

= 2sinxcosx(cos^2 x + cos^2 x)

= 2sinxcosx/(2cos^2 x)

= sinx/cosx

= tanx

You had tan 2x

**Answer this Question**

**Related Questions**

Trig....... - I need to prove that the following is true. Thanks (2tanx /1-tan^x...

Mathematics - Trigonometric Identities - Let y represent theta Prove: 1 + 1/tan^...

Trig - Given: cos u = 3/5; 0 < u < pi/2 cos v = 5/13; 3pi/2 < v < ...

precalculus - For each of the following determine whether or not it is an ...

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

algebra - Can someone please help me do this problem? That would be great! ...

tigonometry - expres the following as sums and differences of sines or cosines ...

MathsSs triG - Consider sin(x-360)sin(90-x)tan(-x)/cos(90+x) 1.A.SIMPLIFY sin(x-...

Trigonometry desperate help, clueless girl here - 2. solve cos 2x-3sin x cos 2x...

trig 26 - simplify to a constant or trig func. 1. sec Ču-tan Ču/cos Čv+sin Čv ...