ABSTRACT
At the end of this chapter, you should be able to:
• State the theorem of Pythagoras and use it to find the unknown side of a right-angled triangle • Define sine, cosine and tangent of an angle in a right-angled triangle • Evaluate trigonometric ratios of angles • Define reciprocal trigonometric ratios secant, cosecant and cotangent • Determine the fractional and surd forms of common trigonometric ratios • Solve right-angled triangles • Understand angles of elevation and depression • Appreciate trigonometric approximations for small angles
Trigonometry is a subject that involves themeasurement of sides and angles of triangles and their relationship to each other. The theorem of Pythagoras∗ and trigonometric ratios are used with right-angled triangles only. However,
there are many practical examples in engineeringwhere knowledge of right-angled triangles is very important. In this chapter, three trigonometric ratios – i.e. sine, cosine and tangent – are defined and then evaluated using a calculator. Finally, solving right-angled triangle problems using Pythagoras and trigonometric ratios is demonstrated, together with some practical examples involving angles of elevation and depression.
