Question

if cosA= -1/2 and π<A<3π/2 then find the value of 4tan^2A-3cosec^2A ?

Answer 1

in QIII, tan is positive and csc is negative. (doesn't really matter, since they're both squared in the expression.) So,

sinA = -√3/2
tanA = √3

csc^2 = 1+tan^2, so

4tan^2-3csc^2 = tan^2A-3 = 0