- #1

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## Homework Statement

prove:

sin3x = sinx (3-4sin^2x)

tanx+sinx/2tanx = cos^2(x/2)

cot2x = (cot^2 x-1)/(2cotx)

## Homework Statement

## Homework Equations

## The Attempt at a Solution

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- Thread starter yvette25
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- #1

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prove:

sin3x = sinx (3-4sin^2x)

tanx+sinx/2tanx = cos^2(x/2)

cot2x = (cot^2 x-1)/(2cotx)

Last edited:

- #2

rock.freak667

Homework Helper

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But anyhow...for the first one...rewrite sin3x as sin(2x+x)

and well for the second and third ones..try simplifying it into sin and cos only , for the last one...remember that cot(x)=1/tan(x)

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