Science, Maths & Technology

### Become an OU student Using a scientific calculator

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# 8 Finding angles from trigonometric ratios

Inverse trigonometric values can be found using the second functions , and of the , and keys. These functions are used in a similar manner to , and .

## Activity 17 Finding angles from trigonometric ratios

Calculate the value of each of the following expressions using your calculator, where possible, giving your answers correct to 1 decimal place.

1. 2. 3. 4. 1. .
If you obtained the answer or 0.5236 (to 4 decimal places), then your calculator is set to work in radians. Make sure that you are working in degrees.
2. (to 1 decimal place).
3. (to 1 decimal place).
4. The calculation is not possible, and your calculator will give a ‘Math Error’. There is no angle whose sine is 2, because the hypotenuse is always the largest side of a right-angled triangle, and hence the maximum value the sine of an angle can be is 1.