I have a question that i am finding a different answer then one given. pleas explain where i am going wrong.

given: cosec Theta = a so i know sin = 1/a

asked to give remaining ratios. terminates in Quadrant 1

cos = sqrt (1-(1/a)^2)

how do they come up with sqrt (a^2-1)/a

i left school too early 22 years ago. college algebra wasn't so bad but this is turning my mind to mush, mental block.

Hope someone can explain this for me. and ill find the reciprocals etc through that.