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Trigonometry: Finding a Missing Angle (Year 9)

Free printable UK Year 9 (Key Stage 3) maths worksheet: use inverse sin, cos or tan to find a missing angle of a right-angled triangle given 2 sides.

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Grade 8 · Math worksheet
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Trigonometry: Finding a Missing Angle

Use an inverse trigonometric ratio (asin, acos or atan) to find the missing angle theta in each right-angled triangle, correct to 1 decimal place.

  1. 1.
    A right-angled triangle has a hypotenuse of 41 and the side opposite angle theta is 24.1. Find theta, correct to 1 decimal place.
  2. 2.
    A right-angled triangle has a hypotenuse of 26 and the side opposite angle theta is 9.3. Find theta, correct to 1 decimal place.
  3. 3.
    A right-angled triangle has a side of 22.3 opposite angle theta and a side of 21.5 adjacent to angle theta. Find theta, correct to 1 decimal place.
  4. 4.
    A right-angled triangle has a side of 19.5 opposite angle theta and a side of 12.2 adjacent to angle theta. Find theta, correct to 1 decimal place.
  5. 5.
    A right-angled triangle has a hypotenuse of 30 and the side adjacent to angle theta is 18.5. Find theta, correct to 1 decimal place.
  6. 6.
    A right-angled triangle has a hypotenuse of 39 and the side opposite angle theta is 12.7. Find theta, correct to 1 decimal place.
  7. 7.
    A right-angled triangle has a side of 17.7 opposite angle theta and a side of 34.7 adjacent to angle theta. Find theta, correct to 1 decimal place.
  8. 8.
    A right-angled triangle has a hypotenuse of 26 and the side adjacent to angle theta is 19.6. Find theta, correct to 1 decimal place.
  9. 9.
    A right-angled triangle has a side of 15.5 opposite angle theta and a side of 4.1 adjacent to angle theta. Find theta, correct to 1 decimal place.
  10. 10.
    A right-angled triangle has a hypotenuse of 19 and the side adjacent to angle theta is 9.5. Find theta, correct to 1 decimal place.
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