16Hit1600
Geometry and TrigonometryMediumSine of a ladder's angle

Geometry and Trigonometry practice question

A 5-metre ladder leans against a wall, and its top touches the wall 4 metres above the ground. What is the sine of the angle between the ladder and the ground?

Answer: 4/5 or 0.8

The ladder is the hypotenuse (5); the height on the wall (4) is the side opposite the angle with the ground. sin = opposite/hypotenuse = 4/5.

Common wrong answers

If you answered 3/5
3/5 is the COSINE: the ladder's foot is 3 metres from the wall, the side adjacent to the angle.
If you answered 4/3
4/3 is the tangent (4 over the 3-metre base).
If you answered 5/4
5/4 is hypotenuse over opposite, the sine upside down.

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