
Yefim S. answered 03/16/21
Math Tutor with Experience
f(7π/4) = 2sec2(7π/4) = 2(√2)2 = 4; tangent point is (7π/4, 4).
f'(x) = 2secxsecxtanx = 2sec2xtanx; Slope of tangent line is f'(7π/4) = 2sec2(7π/4)tan7π/4 = - 4.
So, equation of tangent line is y - 4 = - 4(x - 7π/) or y - 4 = - 4x + 7π