Worked Solution & Mark Scheme (4 marks)
Vertically opposite angle in top triangle = 116° M1
By Cosine Rule: AD² = 9.6² + 2.8² – 2(9.6)(2.8) cos(116°) = 100 + 23.567 = 123.567 M1
AD = √123.567 ≈ 11.1 cm. A1
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Free Printable The cosine rule PDF Worksheets, Revision Guide & GCSE Past Paper Questions (Grade 7)
Download free the cosine rule worksheets (PDF), GCSE maths past paper questions and worked solutions for The cosine rule (7N). This is a Grade 7 geometry topic from the GCSE questions by topic collection for Higher tier GCSE Maths (Edexcel, AQA, OCR and IGCSE).
The free PDF worksheets table below brings together printable question booklets (Qs) and worked answers or mark schemes (Ans) from Maths Genie, Maths4Everyone, Corbett Maths, Maths Made Easy, Dr Frost, 1st Class Maths, Metatutor, Maths Takeaway, Maths DIY, Dr Austin, GCSE Maths Rocket, E Classroom and PMT, along with past paper question booklets.
Below the worksheet links you can read our the cosine rule revision notes and worked examples with diagrams, try real GCSE past paper the cosine rule questions with step-by-step solutions, or download a PDF of all the cosine rule worksheet links.
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Graded exam questions & solutions
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GCSE 9–1 practice booklet & solutions
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Practice Questions & answers
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Textbook Exercise & answers
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MME worksheet & model answers
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GCSE worksheet & solutions
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1st Class Maths (Edxl)
Edexcel exam questions & solutions
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1st Class Maths (AQA)
AQA exam questions & solutions
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Topic worksheet & worked solutions
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Practice questions & answers
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PMT (Edxl)
Edexcel GCSE topic questions & solutions
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PMT (AQA)
AQA GCSE topic questions & solutions
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PMT (IGCSE)
Edexcel IGCSE topic questions & solutions
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Explanation:
Use the Cosine Rule when you do not have a complete opposite side-angle pair: either you know 2 sides and the included angle (SAS) and want the third side using a2 = b2 + c2 − 2bc cos A, or you know all 3 sides (SSS) and want an angle using cos A = b2 + c2 − a22bc.
Make sure the side labeled a is always the side directly opposite the angle A in the formula. Remember to take the square root at the end when finding a side length.
Example 1: Find side a when b = 7 cm, c = 10 cm, and included angle A = 58° (3 s.f.).
Solution:
Example 2: A triangle has sides 6 cm, 8 cm, and 11 cm. Find the largest angle (1 d.p.).
Solution: