# arch tanget

Discussion in 'Homework Help' started by shermaine, Apr 29, 2009.

1. ### shermaineNew Member

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hi,

may i know how to get arch tanget for -1.16?
When in calculator, radian mode, i use tan inver -1.16, but i cant get 2.28

2. ### RoffWell-Known Member

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The tangent function repeats every π radians. For x=arctan(y), Your calculator will give you the principal value, which is located in the interval -π/2 ≤ y ≤ π/2. 2.28 is greater than π/2. Take arctan(-1.16) and add π to the result, and you will get 2.28.

Last edited: Apr 29, 2009

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5. ### shermaineNew Member

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yes, thanks! i got another one, inverse cos of -2/sq root 20, how do i get 242 degree?

6. ### Miles ProwerMember

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You can't.

arccos(-2 / sqrt(20)= 116.565deg

360 - 116.565= 243.435deg