if tan A= n tan B and sin A= m sin B then prove that cos2 A=
atandrit:
complete the question bro, we have to prove cos 2A is equal to what????
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tan A = n tan B
sin A/cos A = n sin B/cos B
m sin B/cos A = n sin B/cos B
m/cos A = n/cos B
∴ cos A = m cos B/n
∵ cos 2A = cos²A - sin²A
∴ cos 2A = (m cos B/n)² - (m sin B)²
= m² cos²B/n² - m² sin²B
= m² (cos²B - n²sin²B)/n ²
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