How do you determine tanthetatanθ given cottheta=-sqrt5/2,pi/2<theta<picotθ=52,π2<θ<π?

1 Answer
Jan 24, 2017

tantheta=-2/sqrt5tanθ=25; sintheta=-2/3sinθ=23; csctheta=-3/2cscθ=32;costheta=-sqrt5/3cosθ=53;sectheta=-3/sqrt5secθ=35

Explanation:

Since tantheta=1/cotthetatanθ=1cotθ, you get:

tantheta=-2/sqrt5tanθ=25

Since sintheta=+-tantheta/sqrt(1+tan^2theta)sinθ=±tanθ1+tan2θ and sine is positive in the second quadrant:

sintheta=+(-2/sqrt5)/sqrt(1+(-2/sqrt5)^2sinθ=+251+(25)2

=(-2/sqrt5)/sqrt(1+4/5)=(-2/sqrt5)/sqrt(9/5)=-2/cancelsqrt5*cancelsqrt5/3=-2/3

Then csctheta=1/sintheta=-3/2

costheta=+-sqrt(1-sin^2theta)

In the second quadrant cosine is negative, then

costheta=-sqrt(1-(-2/3)^2)=-sqrt(1-4/9)=-sqrt(5/9)=-sqrt5/3

and sectheta=1/costheta=-3/sqrt5