## aussy123 Group Title Write the following expression as a function of a positive acute angle. cos 125 one year ago one year ago

1. terenzreignz Group Title

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

2. terenzreignz Group Title

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

3. aussy123 Group Title

why did you use sin

4. terenzreignz Group Title

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

5. aussy123 Group Title

oh sorry

6. terenzreignz Group Title

Get it now?

7. aussy123 Group Title

yes a little

8. aussy123 Group Title

9. terenzreignz Group Title

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

10. aussy123 Group Title

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

11. terenzreignz Group Title

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

12. aussy123 Group Title

Thank you!

13. terenzreignz Group Title

No problem :)