# Math Help - Pathagorian identity

1. ## Pathagorian identity

Write tanΘ in terms of sinΘ if the terminal side of Θ is in quadrant IV.

So far I have cos^2Θ+sin^2Θ=1
cosΘ=+/-sqrt(1-sin^2Θ)

but this is as far as I can get?

2. Cosine is positive in this quadrant, so you should be able to write $\cos\theta=\sqrt{1-\sin^2\theta}$. You can test this with an angel in IV.

$\tan\theta =\frac{\sin\theta}{\cos\theta} = \frac{\sin\theta}{\sqrt{1-\sin^2\theta}}$

3. Thanks! I've got it now.