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**Trigonometry (I) **

**Mathematics SSS 1 Third Term**

**WEEK 5**

**Trigonometry (I) **

**Performance Objectives**

**Students should be able to;**

**Identify ratios forming cosine and tangent of marked angle****Draw right angle triangles****Use right-angle triangles to solve problems involving calculations of lengths**

**Basic Trigonometric Ratios (Sine, Cosine, Tangent, with respect to right-angled triangles)**

**Content**

These trigonometric ratios are applicable to the right-angled triangle. A right-angle triangle is 90^{0}. Thus the remaining two angles add up to 90^{0} since every triangle contains two right angles.

In ∆ABC, B + C = 90^{0}.

Such angles whose sum is 90^{0 }are said to be complementary angles. While capital letters are used for angles, small (lower case) letters are used for sides. Notice that the side opposite A is labelled a, the one opposite B is labelled b etc.

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