Question

How do you figure out the csc(-390deg)?

Thank you very much!

Answer 1

we are going to use the property that sin(-x) = -sinx

and csc x = 1/sinx

csc(-390)
= 1/sin(-390)
= 1/-sin390
= 1/-sin30 , 390 is coterminal with 30
we know sin 30 = 1/2
so
cosc(-390)
= 1/(-1/2)
= -2