Find the exact values of cos 2x and tan 2x if sin x =4/5 and x is a quadrant II angle.

Step-by-step explanation: 3-4-5 triangle

If sinx = 4/5, then cosx = -3/5 and tanx = 4/-3   x is approximately 126.87°

cos2x = cos²x - sin²x = (-3/5)² - (4/5)² = 9/25 - 16/25 = - 7/25

tan2x = 2tanx / (1 - tan²x) = 2(4/-3) / (1 - (4/-3)²) = (8/-3) / (1 - 16/9) = (-8/3) / (-7/9)

tan2x =  (-8/3) • (-9/7) = 72/21 = 24/7

step-by-step explanation:

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