# Use trigonometry to find the perpendicular height of a triangle

## Lesson details

### Key learning points

1. In this lesson, we will identify the perpendicular height of triangles, use trigonometry to find the perpendicular height and apply this to find the area of a triangle.

### Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

## Video

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## Worksheet

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## Starter quiz

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### 3 Questions

Q1.
A ladder leans against a wall. It is 3m away from the wall at an angle of 60 degrees. What is the length of the ladder?
x = 1.5 m
x = 4.70 m
Correct answer: x = 6 m
Q2.
2. A man stands exactly 8m from a lamppost. He looks to the top of the lamppost, as shown. What is the height of the lamppost? Answer to 1 dp
11.9 m
13.4 m
5.4 m
Q3.
Find the perpendicular height of this parallelogram ( to 1 dp)
10 cm
3.5 cm
3.54 cm

## Exit quiz

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### 3 Questions

Q1.
If b is the base, identify the perpendicular height of this triangle.
s
u
Q2.
Find the perpendicular height of the triangle.
0.0333… cm
1 cm