Key learning points

1. The unit circle is a circle with a radius of one.
2. The unit circle is centered on the origin.
3. The sine of an angle is the y-coordinate of the point where the radius has been rotated through that angle.
4. The cosine of an angle is the x-coordinate of the point where the radius has been rotated through that angle.
5. The tangent of an angle is the length of the side opposite the angle along the tangent at x = 1 to the unit circle.

Keywords

• Trigonometric functions - Trigonometric functions are commonly defined as ratios of two sides of a right-angled triangle for a given angle.

• Sine function - The sine of an angle (sin(θ°)) is the y-coordinate of point P on the triangle formed inside the unit circle.

• Cosine function - The cosine of an angle (cos(θ°)) is the x-coordinate of point P on the triangle formed inside the unit circle.

• Tangent function - The tangent of an angle (tan(θ°)) is the y-coordinate of point Q on the triangle which extends from the unit circle.

Common misconception