1.

The minimum value of 3 cosx + 4 sinx + 8 is(A) 5 (B) 9 (C) 7 (D) 3

Answer»

Answer is (D) 

3 cos x + 4sin x + 8 = 5 (3/5 cos x + 4/5sin x) + 8

= 5(sin α cos x + cos α sin x) + 8

= 5 sin(α + x) + 8, where tan α = 3/4



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