Question

Help!

Answer 1

I know how to solve it but i'm not sure how they want me to answer the last one?

Answer 2

@zepdrix ...sorry I keep bugging you xD Do you have time? :)

Answer 3

Ah, yes.
This can be a little tricky ^^

Answer 4

\[\Large\rm \cos^2x-1=-(-\cos^2x+1)=-(1-\cos^2x)\]
And can you apply your square identity from there.
Did those steps make sense? :o

Answer 5

i would solve right side hmm that's easy :D

Answer 6

...haha no I don't get it D:

Answer 7

oo actually yes I do. But what am I meant to do after? factor in the - ?

Answer 8

Where did you get the "cos2x-1" ?
from the last answer?

Answer 9

@zepdrix

Answer 10

we have to prove that \[\huge\rm \cos^2x-1 = -\sin^2\]
^^^^^^^^^^^^^^^^^^^
that's why you should take out "negative 1"