On these unit circles there are degrees on the circle labeled with their coordinates. On the top picture, the numbers labeled on the inside of the circle are the radians. For example, if you look at 30 degrees the sin would be the y coordinate, so it would be 1/2. The cos for this would be the x coordinate, so it would be the square root of 3 over 2. The tan of these is sin over cos, so that would be 1/2 divided by the square root of 3 over 2.