## anonymous one year ago Use the squared Identities to simplify 2cos^2 (x) * cos^2 (x)

1. anonymous

@ganeshie8 @JackJordan

2. anonymous

uhmm... how simple do you want it I mean an easy one would be just 2cos^4(x) lol

3. anonymous

a) 1-cos(4x) / 4 b) 1+4cos(2x)+cos(4x) / 4 c) 1+cos(4x) / 4 d) 1+4cos(2x)-cos(4x) / 4

4. anonymous

@ganeshie8

5. anonymous

are you sure you haven't miswritten the second one?

6. anonymous

b) 1+4cos(2x)+cos(4x) / 4

7. anonymous

thats what i have

8. anonymous

@ganeshie8

9. anonymous

@JackJordan

10. anonymous

@jim_thompson5910

11. anonymous

someone help!

12. hartnn

write both $$\cos^2 x = \dfrac{1-\cos 2x}{2}$$

13. anonymous

It must be a typo... I'm getting 1+4cos(2x)+cos(4x) + 3 / 4 sorry.

14. hartnn

***$$\cos^2 x = \dfrac{1+\cos 2x}{2}$$

15. anonymous

elementary mistake hartnn

16. hartnn

and then expand it.

17. anonymous

So my attempt leads to something similar to B but with +3 at the end. Either I'm wrong (not likely) or the question is wrong.

18. hartnn

then using the same identity you'll need to write $$\Large \cos^2 2x = \dfrac{1+\cos 4x}{2}$$

19. anonymous

ROOKIE MISTAKE!!!

20. anonymous

sorry to everyone. I am so sorry

21. anonymous

So I was right

22. hartnn

so you got it now?

23. anonymous

i must've made a huge typo

24. anonymous

the question is 2sin^2 (x) cos^2x

25. anonymous

sin. not cos. i can't believe i made that mistake.

26. hartnn

okk, then write $$\large \sin^2 x = \dfrac{1-\cos 2x}{2}$$ thats the only difference

27. anonymous

Dang it I knew you made that mistake! Lol, it gives a difference of two squares at the top. I already did that. The answer is a. Can you see why?

28. hartnn

I'd like to see sbsbrand's attempt! :)

29. anonymous

yay it worked! thanks everyone that stayed to help me even tho i wrote the question wrong.......XD