Question

sin (-690)×cos (-300) + cos (-750)× sin (-240)=1 prove that

Answer 1

-sin(690).cos(300)-cos(750).sin(240)
sin(720-30).cos(360-60)-cos(720+30).sin(180+60)
sin30.cos60-cos30.sin60
sin(30-60)
-sin30
-1/2

wait where did I go wrong