Question

If sec3A = cosec (A + 10°) where 3A is an acute angle, then the value of cos(A – 20°) is

Answer 1

Answer:

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Answer 2

Answer:

The value of  cos(A – 20°) is 1

Step-by-step explanation:

sec3A=cosec(A+10°)

3A is an acute angle

cos(A-20°)=?

sec 3A which is equal to cosec(90°-3A)

Apply the value in the given question.

cosec(90°-3A)=cosec(A+10°)

Comparing both sides

cosec gets cancel

90°-3A=A+10°

Comparing both sides

90°-10°=A+3A

80°=4A

4A=80°

A=20°

Substitute the A value to find  cos(A – 20°)

cos(20°-20°)

cos(0°)=1

Hence, the value of  cos(A – 20°) is 1