ABSTRACT
Probably the best-known theorem in geometry, 'Pythagoras's Theorem' applies to right-angled triangles. This chapter describes a right-angled triangle and explains identify the adjacent, opposite and hypotenuse sides, relative to an internal angle of a right-angled triangle. It explores the sine, cosine and tangent of the internal angles of a right-angled triangle, in terms of the ratios of its sides and examines use a scientific calculator to determine the sine, cosine and tangent of any angle. The chapter also describes a scientific calculator to determine an angle, given the value of its sine, cosine or tangent and also examines solve right-angled triangles using the sine, cosine and tangent ratios.
