Trigonometry and Triangles


trigonometry is concerned with the measurement and calculation of the lengths of sides and the sizes of angles of triangles.

there are three basic ratios called the sine, the cosine and the tangent of the angle. these are abbreviated to sin, cos and tan. they are used to find the lengths of sides and angles in right-angled triangles.

greek letters are often used to stand for angles in triangles.

Key Skills

applying the trigonometric ratios to find the lengths of sides and the size of angles in right-angled triangles.


trigonometrytrigonometric ratiossinecosinetangent, right angle,opposite sideadjacent side, hypotenuse.