The SIN , COS and AREA RULE proofs need to be learnt. Go through, learn and practice doing the rules.

Once the proofs are mastered then you will need to apply the rules in application questions.

BUT FIRST LEARN THE PROOFS.

AREA RULE PROOF

WS_AreaRule_23_7_20

COS RULE PROOF

WS_CosRule_23_7_20

SIN RULE PROOF

WS_SineRule_23_7_20