Question

Sin3A=Cos(A-26)
find the value of A?

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Answer 1

We know that sin X = cos(90-X)

So sin 3A = cos(A - 26)

=> cos (90–3A) = cos (A - 26)

=> 90 - 3A = A - 26

=> 90+26 = A + 3A

=> 4A = 116 => A = 116/4 = 29

Answer 2

given us,

3a is an acute angle

sin3a = cos(a - 26)

=> cos(90-3a)= cos(a -26)

=> 90 - 3a = a - 26

=> -3a - a = - 26-90

=> -4a = -116

=> a = -116/-4

=> a = 29

hence, a= 29

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