Hello,

First of all, translate the information you're given :

Since -3/2 < 0 and sin(a) > 0, we have that cos(a) < 0.

Next step, use the most common formula :

(it could have been + sqrt, but since it is negative...)

So substitute this formula of cos(a) into tan(a) and get sin(a) !

Then get cos(a) etc..