Revise trigonometric ratios of sine, cosine and tangent and calculate angles in right-angled triangles with this BBC Bitesize GCSE Maths OCR study guide.

The three trigonometric ratios; sine, cosine and tangent are used to calculate angles and lengths in right-angled triangles. The sine and cosine rules calculate lengths and angles in any triangle.

Use trigonometry. Some rules of trigonometry, such as the law of Pythogoras, apply only for right triangles. However, there are other, more complicated rules for general triangles such as the cosine ...

This means that any complex calculation using classical trigonometry could result in a significant accumulation of errors.