3D trigonometry and Pythagoras

Mark scheme and answers · Total marks: 119

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Question 1 [3 marks]

AG² = AD² + DC² + AE² = 2² + 6² + 3² = 49, so AG = 7.00 cm (3 s.f.).

Question 2 [3 marks]

DC² = AG² - AD² - AE² = 7² - 2² - 3² = 36, so DC = 6.00 cm (3 s.f.).

Question 3 [3 marks]

AD² = AG² - DC² - AE² = 49 - 36 - 9 = 4, so AD = 2.00 cm (3 s.f.).

Question 4 [3 marks]

AE² = AG² - AD² - DC² = 49 - 4 - 36 = 9, so AE = 3.00 cm (3 s.f.).

Question 5 [3 marks]

AG² = AD² + DC² + AE² = 5² + 8² + 4² = 105, so AG = 105 = 10.2 cm (3 s.f.).

Question 6 [4 marks]

In right-angled triangle FCD, FC = CD tan 30°. In the base, AC² = AD² + CD². Triangle AFC is right-angled at C, so tan(angle AFC) = ACFC. Hence angle AFC = 71.7° (1 d.p.).

Question 7 [4 marks]

FC = 5 tan 25°, AC = 12² + 5² = 13. In right-angled triangle AFC, AF² = AC² + FC², so AF = 13.2 cm (1 d.p.).

Question 8 [4 marks]

In right-angled triangle FCD, FC = CD tan 40°, so FC = 7.6 cm (1 d.p.).

Question 9 [4 marks]

FC = 6 tan 35°, AC = 11² + 6² = 157. In right-angled triangle AFC, tan(angle FAC) = FCAC, so angle FAC = 18.5° (1 d.p.).

Question 10 [4 marks]

FC = 8 tan 28°, AC = 6² + 8² = 10. Then angle AFC = 67.0° (1 d.p.).

Question 11 [4 marks]

Let O be the centre of the base. AO = 12 × AB and AE² = AO² + 10². Then cos(angle EAC) = AB²AC · AE with AC = AB2, giving angle EAC = 70.5° (1 d.p.).

Question 12 [4 marks]

With O the centre of the base, AO = AB2 and EA² = AO² + 8², so EA = 9.1 cm (1 d.p.).

Question 13 [4 marks]

Angle EAC = 61.2° (1 d.p.).

Question 14 [4 marks]

EA² = AB²2 + 11² = 812 + 121, so EA = 12.7 cm (1 d.p.).

Question 15 [4 marks]

Angle EAC = 60.5° (1 d.p.).

Question 16 [5 marks]

Let h be the vertical height from P to the base centre. Then h = AB2 tan 65°. Volume = 13 × AB² × h = 1710 cm³ (3 s.f.).

Question 17 [5 marks]

h = AB2 tan 55° with AB = 12, so h = 12.1 cm (3 s.f.).

Question 18 [5 marks]

Volume = 281 cm³ (3 s.f.).

Question 19 [5 marks]

h = 82 tan 48° = 6.28 cm (3 s.f.).

Question 20 [5 marks]

Volume = 1040 cm³ (3 s.f.).

Question 21 [3 marks]

AG² = 6² + 7² + 9² = 166, so AG = 12.9 cm (3 s.f.).

Question 22 [4 marks]

FC = 10 tan 22°, AC = 7² + 10² = 149. Then angle AFC = 71.7° (1 d.p.).

Question 23 [4 marks]

EA² = AB²2 + 6² = 812 + 36, so EA = 8.7 cm (1 d.p.).

Question 24 [5 marks]

h = 102 tan 45° = 52. Volume = 13 × 100 × 52 = 236 cm³ (3 s.f.).

Question 25 [3 marks]

AE² = AG² - AD² - DC² = 12.7² - 5² - 8² = 161.29 - 25 - 64 = 72.29, so AE = 8.50 cm (3 s.f.).

Question 26 [4 marks]

FC = 8 tan 32°, so FC = 5.0 cm (1 d.p.).

Question 27 [4 marks]

Angle EAC = 72.2° (1 d.p.).

Question 28 [5 marks]

h = 112 tan 52°, volume = 13 × 11² × h = 402 cm³ (3 s.f.).

Question 29 [3 marks]

DC² = AG² - AD² - AE² = 13² - 3² - 4² = 169 - 9 - 16 = 144, so DC = 12.0 cm (3 s.f.).

Question 30 [4 marks]

FC = 7 tan 45° = 7, AC = 8² + 7² = 113. Then tan(angle FAC) = FCAC, so angle FAC = 33.4° (1 d.p.).