Question

Evaluate the sine, cosine, and tangent of the angle without using a calculator. θ = − 10π 3

Answer 1

Determine the quadrant adding or subtracting periods -10pi/3+2pi=-4pi/3+2pi=2pi/3
which is the second quadrant because
first quadrant is between 0 and pi/2
second quadrant is between pi/2 and pi
third quadrant is between pi and 3pi/2
fourth is between 3pi/2 and 2pi
now we find the terminal angle since it is the second quadrant we use theta'=pi-theta=pi-2pi/3=pi/3
sin(pi/3)=sqrt(3)/2 sin is positive in the second quadrant
cos(pi/3)=-0.5 cos is negative in the second quadrant
tan(pi/3)=sin(pi/3)/cos(pi/3)=-sqrt(3) tan is negative in the second quadrant