If cos A = 3/5 and the terminal side of angle A lies in quadrant IV, then find tan (A/2)

Answer 1

cosA = 3/5, A = about -53.13 degrees, A/2 = about -26.57 degrees, tan-26.57 = -.5 = -1/2

A is in quadrant IV

sinA = -4/5

tanA = sinA/cosA = -4/3

tan(A/2) = -sqr[(1-cosA)/(1+cosA)]

= -sqr(1-3/5)/(1+3/5)

= -sqr(2/5/8/5)

= -sqr(1/4)

= -1/2 = -0.5