Question

If sin3A = cos(A-26), then what is the value of A? Given that 3A is an acute angle.

A 20 Correct Answer Incorrect Answer
B 21 Correct Answer Incorrect Answer
C 29 Correct Answer Incorrect Answer
D 25 Correct Answer Incorrect Answer
E none of these Correct Answer Incorrect Answer

Solution

Always remember that sin & cos are compliment to each other So sin ɵ = cos( 90-ɵ)  So it is given that sin3A = cos(A-26) Hence 3A + A-26° = 90° So 4A-26° = 90° or 4A =90°+26° =116 or A = = 29°

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