# Math Help - Trigonometry quotient identity?

1. ## Trigonometry quotient identity?

Given: tanX = sinX/cosX

Use the quotient identity and the compound angle formulas for sin (x+y) and cos(x+y) to write a formula for tan(x+y)

2. Originally Posted by ahling
Given: tanX = sinX/cosX

Use the quotient identity and the compound angle formulas for sin (x+y) and cos(x+y) to write a formula for tan(x+y)
Well,

$\sin\left(\alpha + \beta\right)=\sin(\alpha)\cos(\beta)+\cos(\alpha)\ sin(\beta)$

$\cos\left(\alpha + \beta\right)=\cos(\alpha)\cos(\beta)-\sin(\alpha)\sin(\beta)$

Now, what would $\tan\left(x+y\right)$ equal?

--Chris