is it true?

Coterminal angles are the same.

I.e. 240 deg and -120 deg.

then what do you call the 120 degrees going straight line to 300 degrees?

Idk. this thing says they aren't coterminal

http://www.mathopenref.com/coterminal.html

Not sure what you're asking here. But to find co-terminal angles of any given angle, just add or subtract any multiple of 360 to the original angle.
EDIT: So 240 and 60 are not co-terminal angles.

This post was edited by weslee on Nov 5 2013 06:37pm

sec

This post was edited by penoyman on Nov 5 2013 06:46pm

the question is:

Even though 30 degrees and 150 degrees are non-coterminal angles, a calculator will verify that sin 30 = sin 150.


what do they mean "are non-coterminal angles" ????

This post was edited by penoyman on Nov 5 2013 06:51pm

The definition of coterminal means that if you draw a line TO NOT THROUGH the origin at any two coterminal angles, you are drawing the same line.

If you understand that, your question should be answered...

i.e. two coterminal angles are the same angles offset by some multiple of 360 degrees. (0, 360, 720 are all coterminal)

This post was edited by Dontrunaway on Nov 5 2013 07:24pm

so if 120 and 240 are coterminal angles and 30 and 150 are non coterminal angles, what's the difference with that? is it because 120 and 240 are opposite sides? up and down?

120 and 240 are NOT coterminal angles

-120 and 240 are

This post was edited by Dontrunaway on Nov 5 2013 07:40pm