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are you turing them into radiens???

1. csc 90 is a quadruntal angle and your coordnets and 90 are (0,1) since sin takes the y coordinate its 1/sine 1/1 so its 1

2. tan 270, is also a quadruntal angle your coordnites there are (0,-1) and since tan is sin/cos and sin=y and Cos=x its undefined

3 Sin-90 go clockwise 90* instead of counter clockwise (same place as 270) and this one yet again is a quadruntal angle, coordnetes there

are (0,-1) sin takes the Y coornate so sinx=-1

I would solve the problems for you, but I think you can do it yourself with some help. Remember that sine has to do with the y coordinates and that cosine has to do with the x coordinates. Sine of -90 degrees is the same as Sine of 270 degrees. If you look on the circle, 270 degrees corresponds to -1. So Sine of -90 degrees is -1. Tangent is y/x, so look at the coordinates at 270 degrees. Cosec (it's normally written csc) is radius/y and to get the radius you use the pythagorean theorem. I hope this helps. Below, is a picture of the unit circle.

csc 90 = 1/sin 90 = 1/1 = 1

tan 270 = sin 270/cos 270 = 1/0 = undefined

sin -90 = -1 on unit circle (look at unit circle to see)

I hope this helps

the other guy's answer is right, and trust me i know how you feel, im in Pre cal right now and everything goes in one ear and out the other, we had a test today and i failed for sure...any way good luck witht the class.!!