Final answer:
A unit circle is a circle with a radius of 1 unit. Sine and cosine are two circular functions obtained from the unit circle.
Step-by-step explanation:
A unit circle is a circle with a radius of 1 unit. It is used in trigonometry to understand the relationship between angles and the coordinates of points on the circle. The two circular functions obtained from the unit circle are sine and cosine. Sine is the y-coordinate of a point on the unit circle and cosine is the x-coordinate.
For example, at an angle of 30 degrees, the point on the unit circle has coordinates (cos 30°, sin 30°) = (√3/2, 1/2). So, sine of 30 degrees is 1/2 and cosine of 30 degrees is √3/2.