Key learning points

1. Trigonometric functions are derived from measurements within a unit circle
2. The right-angled triangle within the unit circle has a hypotenuse of length one unit
3. The triangle can be scaled to any other right-angled triangle
4. Similar triangles have the same interior angles
5. Similar triangles have the same trigonometric ratios

Common misconception

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.