Question

Write the following expression as a function of a positive acute angle.

cos 125

Answer 1

@aussy123
It might help you to know that with your angle in degrees,
\[\large \cos \ \theta = \sin (90^o - \theta) \]

Answer 2

So
\[\large \cos(125^o)=\sin(90^o - 125^o)=\sin(-35^o)\]

Answer 3

why did you use sin

Answer 4

It's an identity. It didn't say to use a specific function, it just says use a function.

Answer 5

oh sorry

Answer 6

Get it now?

Answer 7

yes a little

Answer 8

the answer is -cos55

Answer 9

I suppose so. You're right :)
It stems from the fact that
it's equal to sin(-35) = -sin(35) = -cos(90 - 35)

Answer 10

I tried that way too, but I also did
cos 125 = cos (180 - 125) = - cos 55

Answer 11

Well, as long as your methods are valid, it should be no problem.

Answer 12

Thank you!

Answer 13

No problem :)