The sling in a crane is the rigging that connects the crane's hook to its load. This rigging may be a metal chain, a mesh or a rope made from synthetic fibres. Engineers need to calculate the angle that the sling makes with the vertical because this angle determines the sling's stress. At a constant load, a larger angle forces additional stress on the sling. Calculate the sling angle from the measurements related to the sling using trigonometry.

- Skill level:
- Easy

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### Things you need

- Tape measure
- Scientific calculator or computer

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## Instructions

- 1
Measure the length of the sling. For example, imagine a sling that measures 3 feet in length.

- 2
Measure the vertical distance that the sling covers. This is the distance between the crane's hook and the load. For example, imagine that this distance is 2 feet.

- 3
Divide the vertical distance by the sling's length: 2 ÷ 3 = 0.67.

- 4
Find the inverse cosine of this ratio using a scientific calculator: cos-1 (0.67) = 47.9 degrees. This is the angle between the sling and the vertical.