Expert: Richard J. Raridon - 1/22/2005

Question
find the exact value of each expression or state that the value is undefined.

1) a. cos 120º
  b. sec 120º
  c. sin 120º
  d. tan 120º
2) a. csc (pi)
  b. tan 2(pi)/3
  c. cot pi/2
  d. sec 5(pi)/6

Answer
Don't you have a calculator, or a table of trig functions?
1) a) cos 120 = -cos 60 = -0.5
b) sec 120 = 1/cos 120 = -2.0
c) sin 120 = sin 60 = 0.866
d) tan 120 = sin 120/cos 120 = -1.732
2) a) csc(pi) = 1/sin(pi) = infinity
b) tan 2(pi)/3 = tan 120 = -1.732
c) cot (pi/2) = cot 90 = 0
d) sec 5(pi)/6 = sec 150 = 1/cos 150  = -1.155