Trigonometry you can see

what does the unit circle have to do with sine and cosine

Sine and cosine come straight from a point moving around a circle: as the point travels, its height above the center traces sine and its horizontal distance traces cosine. Every value between -1 and 1 shows up because that's how far the point can reach vertically or horizontally. This course builds those two functions by watching that point move rather than memorizing a table.

why does a sine graph look like a wave

If you follow the height of a point going around a circle and plot it against the angle, the up-and-down motion stretches out into a repeating wave. The peaks are where the point is at the top of the circle and the troughs where it's at the bottom, so the wave and the circle are the same motion drawn two ways. Seeing the circle turn into the wave is the core idea we start from.

how do you measure an angle going around a circle

An angle can be tracked as a point moves counterclockwise around a circle, starting from the right and sweeping upward. Each position corresponds to a specific height and width, which is what lets you read off trig values for any angle. We treat the angle as motion around the circle so you can picture where any value comes from.

why do sine and cosine repeat over and over

Because the point keeps going around the same circle, once it completes a full trip it returns to where it started and does the exact same thing again. That looping is why the wave never stops repeating and why the same values keep coming back. Watching one full lap makes the repetition obvious instead of mysterious.

what's the easiest way to understand trigonometry visually

Start with one circle and one point moving around it, then watch how its height and width change — nearly everything else in basic trig grows out of that single picture. When the formulas are tied to a moving image, the abstract symbols become something you can actually see. This getting-started course is built entirely around that moving picture.