Find the function values of cos θ, tan θ, sec θ, csc θ and cot θ ?

If sin θ = −(4)/(5)
and cos θ < 0, in which quadrant is θ? Find the function values of
cos θ, tan θ, sec θ, csc θ and cot θ.

1 Answer
Feb 13, 2018

Given that, sin θ = (−4)/(5)

applying the identity, sin^2theta + cos^2 theta = 1

cos^2 theta = 1-sin^2theta

cos^2 theta = 1- ((-4)/5)^2

cos^2 theta = 1- 16/25 = 9/25

costheta = sqrt(9/25) = +-3/5

its given that, cos θ < 0 ; color(magenta)(costheta =(-3)/5
Since, both sintheta and costheta are negative, theta lies in the color(red)("third quadrant").

tantheta = sintheta/costheta
=(-4)/5 xx 5/(-3) => color(magenta)(tantheta= 4/3

sec θ = 1/costheta => color(magenta)(sec theta=(-5)/3

csc θ = 1/sintheta => color(magenta)(csctheta = (-5)/4

cottheta = costheta/sintheta = 1/tantheta => color(magenta)(cottheta=3/4