Question #d2df5

1 Answer
Dec 8, 2017

# +-sqrt3/2.#

Explanation:

We know that, #sin(90^@-theta)=costheta, &, sec^2theta=1+tan^2theta.#

#:. sec^2theta=1+(1/sqrt3)^2...............[because, tantheta=1/sqrt3],#

#=1+1/3=4/3.#

#:. sec theta=+-sqrt(4/3)=+-2/sqrt3.#

# rArr cos theta=+-sqrt3/2.#