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The sine rule and the cosine rule worksheet — GCSE Higher

Fifteen questions on "the sine rule and the cosine rule" — DfE statement G22. Print it, or print three versions so neighbours cannot copy by letter; the key gives the letter for each version.

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The sine rule and the cosine rule worksheet — GCSE Higher

Maths · GCSE Higher · G22 · The sine rule and the cosine rule · 15 questions

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1.A student is asked to rearrange the cosine rule a² = b² + c² − 2bc cos A to make cos A the subject. They write: cos A = (a² − b² − c²) / (2bc). Is the student's rearrangement correct?
(a)Yes — the sign does not matter for cos A.
(b)No — should divide by −2bc, not +2bc; sign is wrong.
(c)No — the denominator should be bc, not 2bc.
(d)Yes — the rearrangement is correct as written.
2.In triangle ABC, AB = 5 cm, BC = 3 cm and AC = 7 cm. Work out the size of angle ABC.
(a)120°
(b)150°
(c)90°
(d)60°
3.In triangle ABC, AB = x cm, AC = (x + 3) cm, BC = 7 cm and angle BAC = 60°. Work out the value of x.
(a)5
(b)37
(c)−8
(d)8
4.In triangle ABC, AB = 7.4 cm, AC = 5.9 cm and angle BAC = 68°. Work out the length of BC. Give your answer to 1 decimal place.
(a)7.5 cm
(b)56.9 cm
(c)11.1 cm
(d)2.9 cm
5.In triangle ABC, AB = 9 cm, AC = 6 cm and angle BAC = 110°. Work out the length of BC. Give your answer to 1 decimal place.
(a)11.6 cm
(b)153.9 cm
(c)12.4 cm
(d)8.9 cm
6.In triangle PQR, PQ = 11 cm, QR = 7 cm and PR = 13 cm. Work out the size of angle PQR. Give your answer to 1 decimal place.
(a)89.6°
(b)32.6°
(c)90.4°
(d)89.8°
7.A triangle has one unknown side or angle, marked x. In which one of these situations should the sine rule, rather than the cosine rule, be used to find x?
(a)Two sides and the included angle; x is the third side
(b)Two sides and the included angle; x is another angle
(c)Two angles and one side are known; x is another side
(d)All three sides are known; x is one of the angles
8.In triangle ABC, BC = 8 cm, AC = 10 cm and angle BAC = 40°. Given that angle ABC is acute, work out its size. Give your answer to 1 decimal place.
(a)53.5°
(b)126.5°
(c)73.2°
(d)30.9°
9.In triangle ABC, AB = 10 cm, BC = 7 cm and angle ACB = 35°. Given that angle BAC is acute, work out the length of AC. Give your answer to 1 decimal place.
(a)7.0 cm
(b)3.4 cm
(c)10.0 cm
(d)14.9 cm
10.In triangle ABC, AB = 8 cm, BC = 11 cm and AC = 6 cm. Work out the size of angle ABC. Give your answer to 1 decimal place.
(a)32.2°
(b)147.8°
(c)102.6°
(d)57.8°
11.Two hikers walk from a campsite A to a lookout B, a distance of 14 km on a bearing of 038°. From B they walk to a shelter C, a distance of 20 km on a bearing of 142°. Work out the direct distance from A to C. Give your answer to 1 decimal place.
(a)34.0 km
(b)21.5 km
(c)23.0 km
(d)27.0 km
12.In triangle ABC, AB = x cm, AC = (x + 2) cm, BC = 15 cm and angle BAC = 100°. Work out the value of x. Give your answer to 1 decimal place.
(a)10.8
(b)9.6
(c)10.6
(d)8.8
13.A drone flies from base station D on a bearing of 065° for 14 km to a checkpoint E. At E it changes course and flies on a bearing of 165° for 20 km to a delivery point F. Work out the direct distance from D to F. Give your answer to 1 decimal place.
(a)23.4 km
(b)498.8 km
(c)22.3 km
(d)26.3 km
14.A ship leaves port P and sails 24 km on a bearing of 040° to a buoy Q. It then sails 31 km on a bearing of 115° to a lighthouse R. Work out the direct distance from P to R. Give your answer to 1 decimal place.
(a)33.9 km
(b)43.8 km
(c)55.0 km
(d)19.9 km
15.Which of these statements about solving a triangle is correct?
(a)Two sides + a non-included angle: cosine rule gives the angle directly.
(b)Two sides + angle between them: use the sine rule.
(c)All three sides: use the sine rule for any angle.
(d)Two angles and a side: sine rule finds other sides.

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