I am doing a GCSE maths foundation paper for revision and one question has a triangle with the base side being 9cm and the other 2 sides 7.5cm. Is there a formula for finding the angles of the triangle given the lengths of each side so that the 2 side lengths join together at the top to complete the triangle?




Use cosine formula of triangles

$$\cos A=\frac{7.5^2+7.5^2-9^2}{2\cdot7.5\cdot 7.5}$$

  • $\begingroup$ Hi could you explain what's happening here and how I get the angles to form the triangle? $\endgroup$ – crmepham Jun 9 '13 at 14:49
  • $\begingroup$ @crm, follow the link and you'll get a picture. $\endgroup$ – vadim123 Jun 9 '13 at 14:59

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