Lesson: Finding the Area of a Triangle Using Trigonometry Mathematics

In this lesson, we will learn how to find the area of a triangle using the lengths of two sides and the sine of the included angle.

Lesson Plan

Students will be able to

derive and recall the formula ,
use the formula to calculate the area of a triangle given two of its lengths and an included angle,
calculate unknown lengths or angle measures given the area of a triangle,
calculate areas of parallelograms and other compound shapes using the formula.

Q1:

Which of the following is a formula that can be used to find the area of a triangle?

Q2:

In the given figure, work out the area of the triangle to 2 decimal places.

Q3:

A small triangular flower bed has measurements as shown in the diagram. Calculate its area in square feet. Give your answer to two decimal places.