Question

Can someone explain this to me.. *Quadrantal Angles*

Any angle whose measure is a multiple of 90, 180, or 270 is called a quadrantal angle.

I was told in my homework to find which ones equaled 0, 1, -1, and undefined. But my work was completely off from the answers.

I know that r always = 1 for quadrantal angles. Here is what I did..


Select the functions that have a value of 0. (For 0degrees.)

x=0 y=0 r=1 (I got x&y by the point they would be on the axis of the graph)

sin0degrees=(y/r)=(0/1)=0
cos0degrees=(x/r)=(0/1)=0
tan0degrees=(x/y)=(0/0)=undefined
cot0degrees=(x/y)=(0/0)=undefined
sec0degrees=(r/x)=(1/0)=undefined
csc0degrees=(r/y)=(1/0)=undefined

I thought I had all those right & My answer I gave was sin & cos. But apparently I was wrong and the answer was sin & tan.

I'm not sure where I messed up at, can someone please help me ?? Thanks so much!

Answer 1

If what I said doesn't make sense, I can try to re-explain my thinking. Thanks again!

Answer 2

cos(0)=1

Answer 3

tan 0 = 0

Answer 4

tan 180 = 0
tan 90 is undefined
tan 270 is undefined

Answer 5

Think 'Unit Circle'

Answer 6

Oh, I think where I went wrong was that my x & y's weren't right. I was saying (0,0) not (1,0)

Answer 7

Yeah, (0,0) is the origin and isn't on the circle.

Answer 8

Oh okay, that makes more sense

Answer 9

But for 90, I got (0,1) like you did on your circle, and I still got things wrong..

Answer 10

Oh wait, no I didn't. Whoops!

Answer 11

The points are (x,y)=(cos,sin)
at 90º . . .
See it now?

Answer 12

Yes, I do. Thank you so much. I really really appreciate it!!!!

Answer 13

Pro tip: whenever you are doing trig stuff, draw a unit circle.

Answer 14

Okay, I definitely will from now on. Thanks again :)