- #1

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- 92

## Homework Statement

cos(2tan

^{-1}(1/7)) equals-

a)sin(4cot

^{-1}3)

b)sin(3cot

^{-1}4)

c)cos(3cot

^{-1}4)

d)sin(4cot

^{-1}4)

## Homework Equations

## The Attempt at a Solution

I am completely stuck in this one. I tried using the formula [itex]2tan^{-1}x=tan^{-1}(\frac{2x}{1-x^2})[/itex]. Using this formula i got [itex]cos(tan^{-1}\frac{7}{24})[/itex].

Now i am stuck, i can't think of anything else on how to proceed.

Any help is appreciated. :)