# If sin 3A = cos (A – 26°), where 3A is an acute angle, find the value of A.

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If sin 3A = cos (A – 26°), where 3A is an acute angle, find the value of A.

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Solution : We are given that sin 3A = cos (A – 26°). ---------(1)
Since sin 3A = cos (90° – 3A), we can write (1) as
cos (90° – 3A) = cos (A – 26°)
Since 90° – 3A and A – 26° are both acute angles, therefore,
90° – 3A = A – 26°
which gives A = 29°