Posted by Anonymous on .
Determine if the value of each trig function is positive, negative, zero, or undefined.
a) tan 310 degrees
b) cos 7pi/6
c) sin -245 degrees
d) sec( -7/2)
Determine in which quadrant you are in,
then use the CAST rule
= sin( 115°) , (going 115 counterclockwise is the same as going 245° clockwise )
115° is in quad II
in quad II , sine is positive, so
sin(-245°) is positive
you can always check with your calculator.
in sec(-7/2) , remember that if no units are stated, radians are assumed.
so -7/2 is coterminal with 2π - 7/2 which is appr 2.78