Trigonometric Ratios  
Summary 
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 thetangent of the angle. these are abbreviated to sin, cos and tan. greek letters are often used to stand for angles in triangles. 

Key Skills 
apply the trigonometric ratios to find the lengths of sides and the size of angles in rightangled triangles. 

Vocabulary 
