# Homework Help: Use power-reducing formulas to rewrite

1. Oct 11, 2012

### AlisonWagner

1. The problem statement, all variables and given/known data
Use power-reducing formulas to rewrite 152sin^2 x cos^2 x

2. Relevant equations
sin^2θ= 1-cos2θ/ 2 and cos^2θ= 1+cos2θ/2

3. The attempt at a solution
152(1-cos2x/2)(1+cos2x/2), 152/4 (1^2 - cos^2 2x), 30(1-(1+cos4x/2), and I got 30-30+30cos4x/2 as the answer but the answer is supposed to be 19-19 cos4x. I have no idea how that can be?

2. Oct 11, 2012

### tiny-tim

Welcome to PF!

Hi Alison! Welcome to PF!

(try using the X2 button just above the Reply box )
Nooo

(but anyway wouldn't it be simpler to start with sin2xcos2x = (sinxcosx)2 ? )

3. Oct 11, 2012

### LCKurtz

$\frac{152} 4 = 38$.

4. Oct 11, 2012

### AlisonWagner

Re: Welcome to PF!

and then what would I do after that? Because I know we are supposed to use the power reducing formulas to solve it

5. Oct 11, 2012

### AlisonWagner

Ooh well I guess doing the right math would help me get that...haha thanks for pointing that out! Now I know my mistake!