# Inverse Circular Function, help!!!

• Aug 23rd 2008, 05:04 PM
nee
Inverse Circular Function, help!!!
y=cot-1(-.92170128)
• Aug 23rd 2008, 05:14 PM
Spec
What's the question exactly?
• Aug 23rd 2008, 05:24 PM
nee
According to the text the answer should come up to 2.3154725 in radian mode.

The text states: "We take the inverse tangent of the reciprocal to find the inverse cotangent".

I therefore punch in:

tan-1(1/-0.92170128)

like the examples show me but I get:

-0.826120119
• Aug 23rd 2008, 05:39 PM
Spec
You were using the correct method: $\displaystyle cot^{-1}(z) = tan^{-1}(\frac{1}{z})$

The book's answer is $\displaystyle -0.826120119 + \pi$

I should probably mention that they've given this answer because arccotangent's range is $\displaystyle 0 < y < \pi$
• Aug 23rd 2008, 05:43 PM
nee
OK I just fugured it out:

In degree mode I punched in:

tan-1(1/-0.92170128)
= -47.33319621

-47.33319621 + 180 (which is ∏ radians)
= 132.6668038

132.6668038/180
= 0.737037799

0.737037799 x
= 2.31572534

but I can't fugure out how to get the answer strait into radians?
• Aug 23rd 2008, 05:45 PM
nee
Oh ok. Thanks Spec, I was almost there.

nee