Find Points on the Unit Circle Given Angles in Radians

This video explains how to corresponding points on the unit circle given positive and negative angles in radians.

[avathomas]

im in precal and i am struggling :')

[mashihodpotatoetm]

Still don't understand how you get it without a graph like this. Our module straight up gave us an activity that asks us to find the coordinates without giving us a single clue how to.

[xVoidCypher]

So for the example -9pi/4 ..I get how to convert from radians to degrees and I understand that -405 degrees is one full rotation, plus another -45 degrees which when subtracted from a full 360 degrees leaves us with the angle for 315 degrees, but how would you calculate that in terms of pi?
2pi=1 full rotation, and another 45 degree turn in pi would be pi/4 degrees, so what operations would you perform here to solve for that?

[TheJimmyDonut]

For better explanations, check out "The Organic Chemistry Tutor". After watching this video 3 times, all I could hear is "Piridians" :(