Answer:
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
