Use a calculator to approximate 2 values of feta (positives only) of cos[feta]=.8746
Round to 2 decimal places.

Question

Use a calculator to approximate 2 values of feta (positives only) of cos[feta]=.8746
Round to 2 decimal places.

agent0smith · Answer

Do you mean theta? cos(feta) = cheese

(...because feta = cheese)

$$\cos \theta = 0.8746$$
take the inverse cosine of both sides
$$\cos^{-1} \cos \theta = \cos^{-1} 0.8746$$

$$\theta = \cos^{-1} 0.8746$$

anonymous · Answer

Ahaha yes sorry.
I did that and I got 29 degrees and from previous problems you're suppose to add or subtract 180 since they asked for 2 values. I'm confused on that part.

agent0smith · Answer

Since you want positives, you can add multiples of 360, or subtract 29 degrees from 360.

anonymous · Answer

Wait, I'm having a hard time understanding..why not 180?

agent0smith · Answer

Try adding 180 to 29... cos209 = -0.8746 (not 0.8746)

anonymous · Answer

OHHHHHHHHH THANK YOU SO MUCH!!

agent0smith · Answer

No prob.

cos (360° − x) = cos x

but

cos (180° + x) = − cos x

anonymous · Answer

Thanks!! That^ helped alot too.

agent0smith · Answer

and also cos (360° + x) = cos x

That one applies to sine/tan too (since adding multiples of 360 is just going around the circle in whole rotations, so the 'reference angle' stays the same)

anonymous · Answer

Thanks :)