Question

if A=60°,B=30° then prove that cos (A+B)=cosA×cosB-sinA×sinB​

Answer 1

LHS

Cos(A+B)= Cos (60+30)=Cos(90)=0

RHS

Cos60×Cos30-Sin60×Sin30

1/2×√3/2 - √3/2 ×1/2

=0

LHS=RHS

Hence prove

Answer 2

Answer:

Cos 90=1-1

Cos 90=0

LHS=RHS

Step-by-step explanation:

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