Trig help

[Netzer7]

Use a double-angle or half angle identity to find the exact value to solve these two problems. Please help I'm confused about how to convert CSC to sin and tan to CSC.
http://prntscr.com/nxpa3t

 

[pka]

I can help with the second: $\displaystyle \tan(\theta)=\frac{3}{4};~\pi\le\theta\le\frac{3\pi}{2}$ find $\displaystyle \csc(2\theta)$
Note that $\displaystyle \theta\in\text{Quad}III$. Thus $\displaystyle \sin(\theta)=\frac{-3}{5}~\&~\cos(\theta)=\frac{-4}{5}$
\(\displaystyle \begin{align*}\csc(2\theta)&=\frac{1}{\sin(2\theta)} \\&=\frac{1}{2\sin(\theta)\cos(\theta)}\\&\text{can you finish ?} \end{align*}\)

 

[Netzer7]

I can help with the second: $\displaystyle \tan(\theta)=\frac{3}{4};~\pi\le\theta\le\frac{3\pi}{2}$ find $\displaystyle \csc(2\theta)$
Note that $\displaystyle \theta\in\text{Quad}III$. Thus $\displaystyle \sin(\theta)=\frac{-3}{5}~\&~\cos(\theta)=\frac{-4}{5}$
\(\displaystyle \begin{align*}\csc(2\theta)&=\frac{1}{\sin(2\theta)} \\&=\frac{1}{2\sin(\theta)\cos(\theta)}\\&\text{can you finish ?} \end{align*}\)

Yes i worked through this question and have closed it since thank you though