Right-angled triangles (that is triangles where one of the angles is 9 0 ∘ ) are the easiest topic for introducing trigonometry. Since the sum of the three angles in a triangle is 18 0 ∘ it follows that in a right-angled triangle there are no obtuse angles (i.e. angles greater than 9 0 ∘ ). In this Section we study many of the properties associated with right-angled triangles.


Learning Outcomes

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