anonymous 3 years ago Write the following expression as a function of a positive acute angle. cos 125

1. terenzreignz

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

2. terenzreignz

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

3. anonymous

why did you use sin

4. terenzreignz

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

5. anonymous

oh sorry

6. terenzreignz

Get it now?

7. anonymous

yes a little

8. anonymous

9. terenzreignz

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

10. anonymous

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

11. terenzreignz

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

12. anonymous

Thank you!

13. terenzreignz

No problem :)