In the diagram give, AC = BC = 1, CD = n and angles ABC = $\displaystyle \theta$, BAD = $\displaystyle \beta$.

i) Prove that: tan $\displaystyle \theta $= $\displaystyle \frac{1 - n}{1 + n}$tan$\displaystyle \beta$

ii) What type of triangle is ABD in the case where n= 1?

Could someone please show me how to do this question? I dont get it at all.