Unit Circle and Trig Value Signs
A unit circle is a circle with a radius of one (a unit radius). In trigonometry, the unit circle is centered at the origin.
For the point (x,y) in Quadrant I, the lengths x and y become the legs of a right triangle whose hypotenuse is 1.
By the Pythagorean Theorem, we have x2 + y2 = 1
