The known function f (x) = (1-sin2x) / cosx Let α be the angle of the fourth quadrant and Tan α = - 4 / 3

The known function f (x) = (1-sin2x) / cosx Let α be the angle of the fourth quadrant and Tan α = - 4 / 3

tana=-4/3
sina=-4/5
cosa=3/5
f(a)=(1-sin2a)/cosa=(1-2sinacosa)/cosa=(1-2*(-4/5)*3/5)/(3/5)=49/15