How is it possible to simplify:
cos(alpha)(-1) possibly using an identity?

Question

How is it possible to simplify: 
cos(alpha)(-1) possibly using an identity?

perl · Answer

it is hard to say what this represents , is this an equation or inverse cosine

anonymous · Answer

this is the last part of my question all I need is to simplify unless this is the most it may be simplified

anonymous · Answer

$$\cos(180+\alpha)$$

perl · Answer

we can simplify that,

perl · Answer

you can actually apply the cos angle sum formula
cos (x + y) = cos(x) * cos(y) - sin(x)*sin(y)

anonymous · Answer

how.... I don't want a final answer, just help on getting there.

perl · Answer

cos(180 + a) = cos(180)*cos(a) - sin(180)*sin(a)

anonymous · Answer

okay, and I have. It's suppose to be done in terms of alpha

perl · Answer

a = alpha

anonymous · Answer

i understood what you ment I just didn't want to go to the specific menu....

perl · Answer

yeah i hate the latex menu myself :D

anonymous · Answer

the question states to answer it in terms of Alpha and i came to: $$\cos(\alpha)(-1)$$

perl · Answer

right, do you see why?

anonymous · Answer

yes, but is it possible to simplify or is that the final step?

perl · Answer

cos(180 + a) 
= cos(180)*cos(a) - sin(180)*sin(a)
= (-1)*cos(a) - 0 * sin(a)
= -cos(a)

anonymous · Answer

ohhhhh okay. I understand :) thanks