As you may see, I am struggling at this.

Show that, for triangle RST, t = r sin (alpha + beta)/sin alpha

iv tried using the sine rule,

t/sin(180 - alpha - beta)=r/sin alpha

t = r / sin alphaxsin(180 - alpha - beta)

After that, i get confused because usually i would expand the sin bracket. ie:

sin(45+45) = sin 45 cos 45 + cos 45 sin 45

but in this case, i have 180, alpha, and beta in one bracket.......

Am i even taking the right steps?

Please help.