Answer:
Sin A= Cos B
Explanation:
Doing each equation out, using sohcahtoa (sin=opposite/hypotenuse, cos=adjacent/hypotenuse, tan=opposite/adjacent, we don't need tan for this problem), we get Sin A=BC/AB, Sin B=AC/AB, Sin C=1, Cos A=AC/AB, Cos B=BC/AB. Afterwards we see which pairs are equal.... Sin B= Cos A, Sin A=Cos B. The final step is seeing which answer matches the multiple choice options. The only option that works is Sin A=Cos B. Hope this helps!