# Use inverse functions to find an angle

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## Lesson details

### Key learning points

- In this lesson, we will find a missing angle in a given triangle using the inverse trigonometric functions. We will need to interpret which trigonometric ratio to use, and rearrange it.

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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.

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### 3 Questions

Q1.

Use your calculator find the value of cos(56) to 3 decimal places.

0.560

0.829

Others

Q2.

Use your calculator find the value of tan(89) to 3 decimal places.

1.000

Error

Others

Q3.

3. Use your calculator to work out the size of sinѲ = 0.21 . Give your answer to one decimal place.

21.0 degrees

Error

Others

### 3 Questions

Q1.

Which of the trigonometry ratios will be required to find the missing angle in this question?

inverse cosine

inverse tangent

Q2.

Find the missing angle, giving your answer to 1 decimal place.

60 degrees

72.1 degrees

Q3.

Find the missing angle, giving your answer to 1 decimal place.

27.6 degrees

48.4 degrees