An isosceles triangle with angles of 100°, 40° and 40° is an obtuse-angled triangle. Image caption, A scalene triangle with one angle greater than 90° is an obtuse-angled triangle.

Discusses the properties and types of triangles, explaining that a triangle is a closed figure with three sides and angles. It categorizes triangles into equilateral, isosceles, scalene, obtuse ...

Isosceles triangle. An isosceles triangle is a triangle that has two equal sides and two equal angles. The two equal angles always occur where the third non equal side meets one of the equal sides.