How to find the height of an oblique triangle with the area

The height of a triangle can be found in different ways, depending on the type of triangle and the information you have or measure. Rectangular triangles, which include a 90-degree angle, are the easiest to measure using the Pythagorean theorem (if the lengths of two sides are known) or the formula of the area (if the area and the base are known). Equilateral triangles, in which all sides are of equal length, and isosceles triangles, in which three of their sides are of equal length, can be cut in half, creating two right triangles. The oblique triangles, those that do not have the interior angle equal to 90 degrees, are more difficult, and require trigonometry to find their height. Next, we will calculate the height of an oblique triangle using the formula of the area

You will need to:
  • Scientific calculator
  • Conveyor
  • Ruler
Steps to follow:

one

Draw the triangle and name the sides and known values. [A, B and C are the angles. a, b, c are the sides, where C is the base, h is the height. In this example, A = 60 degrees and b = 5.]

two

Write the area formula, A = 1/2 bh (A = area, b = base, h = height). All values ​​do not have to be known, but the formula helps keep everything oriented correctly.

3

Find the side adjacent to the base. [side b = 5]

4

Find the angle adjacent to the base and the side in step 3. If you do not know, a protractor will help you measure the angle . [angle A = 60]

5

Write the formula for the height, which is the side adjacent to the base multiplied by the sine of the angle adjacent to the side. [h = 5sin60]

6

Perform the calculations to find the height. [h = 5 x 0.87 = 4.33]

Tips
  • The base can be either side of the triangle.
  • The trigonometry method (using sine) can be applied to right triangles as well.
  • The three angles of a triangle must add up to 180 degrees.