Cambridge IGCSE Mathematics · Syllabus 0580 · Trigonometry
Right-Angled Triangles
What is Right-Angled Triangles?
Triangles containing an angle of ninety degrees, in which each acute angle is linked to two of the three sides by the ratios sine, cosine and tangent: sine is opposite over hypotenuse, cosine is adjacent over hypotenuse and tangent is opposite over adjacent. The labels opposite and adjacent are defined relative to a chosen reference angle and swap when the other acute angle is chosen, while the hypotenuse, opposite the right angle, never changes. These ratios, with Pythagoras' theorem, solve two-dimensional problems, and knowledge of three-figure bearings may be required; all of that is examined on both the Core and the Extended route. The Extended route adds two further requirements to the same topic row: knowing that the perpendicular distance from a point to a line is the shortest distance to that line, and carrying out calculations involving angles of elevation and depression.
This definition is part of the Trigonometry chapter in Cambridge IGCSE Mathematics.