Area of a Triangle - Areas of Polygons and Circles

Geometry: Area of a Triangle - Areas of Polygons and Circles

This is a free lesson from our course in Geometry


	In this lesson, we will look at the formula used to calculate the area of a triangle. You will learn it with the help of some examples and practice questions with solution, using video explanations by the instructor. You will look at some of the formulas used to calculate the areas of triangles. If the base of a triangle is b and the height is h, then the area of the triangle is: 1/2 x base x height. (More text below video...)

Other useful lessons:

Area of a Rectangle

Area of a Square

Area of a Trapezoid

Area of a Rhombus

Area of a Parallelogram

Area of a Circle

Effect of dimension changes on Area

Real World Applications - Area of Polygons and Circles

(Continued from above) E.g. if base of a triangle is 20 cm and height 10cm, then calculated area using above formula is 1/2 x 20 x 10 = 100 cm². If base of the triangle and its area is known, then height is given by: height = 2 x Area/Base. E.g. if the area of a triangle is 300 cm² and height is 10 cm, then base is 60 cm.
If three sides of a triangle a, b, c are given, we can use Heron's formula:
Area =

((s)(s - a)(s - b)(s - c)) where s= (a + b + c)/2
Given the lengths of two sides of a triangle a, b and the measure of angle C between them, the following formula can be used: Area of triangle = 1/2 ab sin C .

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