Introduction to Trigonometry

In a right triangle ABC

In a right triangle ABC with right angle at B, for angle A: sin A = opposite/hypotenuse (BC/AC), cos A = adjacent/hypotenuse (AB/AC), tan A = opposite

Specific trigonometric values for important angles

Specific trigonometric values for important angles: sin 0° = 0, sin 30° = 1/2, sin 45° = 1/√2, sin 60° = √3/2, sin 90° = 1. Similar patterns exist for

Fundamental relationships that are always true

Fundamental relationships that are always true: sin²A + cos²A = 1, sec²A - tan²A = 1 (for 0° ≤ A < 90°), cosec²A - cot²A = 1 (for 0° < A ≤ 90°). Also,

The values of trigonometric ratios depend

The values of trigonometric ratios depend only on the angle, not on the size of the triangle. This is because all right triangles with the same acute