This task assumes that students can find either side of a triangle using the Tan ratio, find the angle using the Tan ratio and know Pythagoras.  It is designed to help students focus their attention on the subtle differences in the algebra of calculating the opposite or adjacent sides.  The inclusion of Pythagoras is designed to help pupils assimilate trig and Pythagoras in their mental schema and deal with the redundant information given.  

I have used it before introducing Sin and Cos ratios.  

Credit:  @chrismcgrane84