How do you calculate the inverse cosine, inverse sine, or inverse tangent without a calculator?
Example: cos^-1(1)

Question

How do you calculate the inverse cosine, inverse sine, or inverse tangent without a calculator?
Example: cos^-1(1)

nory · Answer

Oh, you mean $$\cos^{-1} 1$$ ?

zzr0ck3r · Answer

well cos(?) = 1?

nory · Answer

What number has a cosine of 1? (There are actually infinite solutions. Just choose the simplest one.)

anonymous · Answer

Yeah, sorry, I meant what Nory typed, I just didn't know how to type it XD

zzr0ck3r · Answer

cos(0) = 1, cos(2pi) = 1, ....cos(0+-2pin) = 1

anonymous · Answer

Oh! I think I get it now. So basically I'm just using the unit circle?

nory · Answer

I don't know what methods you've been taught to use...
The way I do these problems in general is I ask myself, "What number has a cosine" (if I'm doing inverse cosine) "of so-and-so?"

anonymous · Answer

Okay! That helps A LOT! Thank you so much!

anonymous · Answer

Remember, however the limitations the inverse of a function has. cos^-1(x) for instance, in order to be an inverse of a FUNCTION, has to be one-to-one. so the values for cosx=1, the x has to fall within the domain of the inverse. For the inverse of cos, your answer has to be given in the range of its x, or cos's range, being: [0,pi]  just a heads up