The question I don't get is:

"For which of the trigonometric points defined in the previous question is it impossible to calculate:

a) the tangent?

b) the cosecant?

c) the secant?

d) the cotangent?"

the previous question was:

"Without using a calculator, give the coordinats of the trigonometric point corresponding to a central angle that measures"

a) 0°b) -90

°

c) 180°

d) -270°

e) -360°"

Any help would be GREATLY appreciated!

Thanks!