unit circle!

I understand the unit circle, however how do you know that sin90=1 and cos(-90)=0 I don't quite understand how that works...

I understand the unit circle, however how do you know that sin90=1 and cos(-90)=0 I don't quite understand how that works...

I'm not sure I understand the question. The unit circle is a method for demonstrating sines and cosines parametrically as x² + y² = 1
x = cos(t) and y = sin(t)
Looking at the circle at certain x and y coordinates you can see that this is true.

Because $sin\theta=\frac{O}{H}$ and $cos\theta=\frac{A}{H}$. This is dues to the SOH-CAH-TOA rule.

in the book it says sin90=1 because p has coordinates (0,r) so sine =r/r. How do you know that P has those coordinates sine I do not know what sine 90 looks like on the unit circle.

Read the above post. The hypotenuse = 1. The sides are x and y

sorry that does not help, but I have read elsewhere an have figured it out

Are you OK with this now?

Yes with that but just one question, it says given that theta is an angle measured in degrees, express in terms of sine theta: sin(-360+theta) I understand how to work this out, but I thought the answer was -sine theta rather than +sine theta ??