If sin 2A= cos(A+30)°, then the measure of angle A is _______
[ 20° , 30°, 40°, 70°]
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Answer:
20°
Step-by-step explanation:
Sin and Cos are complementary angles and can be written as
Sin A = Cos (90-A)
So, Sin 2A = Cos (A+30) can be written as
Cos (90-2A) = Cos (A+30)
(we substitute Sin 2A = Cos (90-2A) in the above equation)
Therefore, 90-2A = A+30
3A = 60
A = 20°
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