Need help evaluating:

cos(tan^-1(-5/2))

Question

Need help evaluating:

cos(tan^-1(-5/2))

jim_thompson5910 · Answer

First draw a right triangle with angle theta

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anonymous · Answer

You have already asked many similar questions, didn't you try to learn ?

anonymous · Answer

yes i have tried but i keep getting confused.

jim_thompson5910 · Answer

If we let 

theta = tan^-1(-5/2) 

then

tan(theta) = -5/2

this implies that theta is either in quadrant 2 or quadrant 4 (because tan(theta) is negative in these quadrants)

anonymous · Answer

would i have to pick one quadrant or does it not matter?

jim_thompson5910 · Answer

it should say how theta is restricted

jim_thompson5910 · Answer

anyways, let's just focus on the positive version of both numbers

so if tan(theta) = 5/2, then

tan(theta) = opp/adj = 5/2

making the opposite side 5 and the adjacent side 2

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jim_thompson5910 · Answer

what is the hypotenuse?

anonymous · Answer

would i do 5^2+2^2=c^2 or 5^2-2^2=c^2?

jim_thompson5910 · Answer

you use a^2 + b^2 = c^2

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