Q. 6 A5.0( 2 Votes )

If A=60o and B = 30o, verify that :

cos (A+B) = cos A cos B – sin A sin B

Answer :

Given: A=60o and B =30o

Now, LHS = Cos (A+B)


Cos (60 o + 30 o)


Cos (90 o)


0 [ cos 90 o = 0]


Now, RHS = Cos A Cos B – Sin A Sin B


cos(60 o) cos(30 o) – sin(60 o) sin (30 o)



0


LHS = RHS


Hence Proved


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