This discussion is now closed.
Scroll to see replies
\displaystyle (1-\lambda -\mu )\mathbf{a} + \lambda\mathbf{b} + \mu\mathbf{c} = \mathbf{a} - \lambda\mathbf{a} - \mu\mathbf{a} + \lambda\mathbf{b} + \mu\mathbf{c} \\[br]\mathbf{r} = \mathbf{a} + \lambda (\mathbf{b} - \mathbf{a}) + \mu (\mathbf{c} - \mathbf{a}) \longleftarrow \text{Plane through }\mathbf{a}. \\[br]\text{Let } \mathbf{n} = (\mathbf{b} -\mathbf{a})\cross (\mathbf{c} -\mathbf{a}) = \mathbf{b}\times\mathbf{c} - \mathbf{a}\times\mathbf{c} - \mathbf{b}\times\mathbf{a} = \mathbf{a}\times\mathbf{b} + \mathbf{b}\times\mathbf{c} + \mathbf{c}\times\mathbf{a}. \\[br]\text{Then }\mathbf{r}\cdot\mathbf{n} = \mathbf{a}\cdot\mathbf{n} . \\ \\[br][br][(1-\lambda -\mu )\mathbf{a} + \lambda\mathbf{b} + \mu\mathbf{c}]\cdot(\mathbf{a}\times\mathbf{b} + \mathbf{b}\times\mathbf{c} + \mathbf{c}\times\mathbf{a}) = \mathbf{a}\cdot (\mathbf{a}\times\mathbf{b} + \mathbf{b}\times\mathbf{c} + \mathbf{c}\times\mathbf{a})\\[br](1-\lambda -\mu )\mathbf{a}\cdot\mathbf{b}\times\mathbf{c} + \lambda\mathbf{b}\cdot\mathbf{c}\times\mathbf{a} + \mu\mathbf{c}\cdot\mathbf{a}\times\mathbf{b} = \mathbf{a}\cdot\mathbf{b}\times\mathbf{c} \text{ and first result follows}. \\[br]\bigg[\mathbf{r}\cdot\mathbf{n} =\bigg] \mathbf{a}\cdot\mathbf{n} = \mathbf{b}\cdot\mathbf{n} = \mathbf{c}\cdot\mathbf{n} \\[br]\mathbf{a}\cdot(\mathbf{a}\times\mathbf{b} + \mathbf{b}\times\mathbf{c} + \mathbf{c}\times\mathbf{a}) = \mathbf{b}\cdot(\mathbf{a}\times\mathbf{b} + \mathbf{b}\times\mathbf{c} + \mathbf{c}\times\mathbf{a}) = \mathbf{c}\cdot(\mathbf{a}\times\mathbf{b} + \mathbf{b}\times\mathbf{c} + \mathbf{c}\times\mathbf{a} ). \\[br]\mathbf{a}\cdot(\mathbf{b}\times\mathbf{c}) = \mathbf{b}\cdot(\mathbf{c}\times\mathbf{a}) = \mathbf{c}\cdot(\mathbf{a}\times\mathbf{b}) \text{ as the dot product of two perpendicular vectors is }\mathbf{0}. \\[br]A, B, C, O \text{ all in same plane }\Rightarrow \mathbf{a}\cdot (\mathbf{b}\times\mathbf{c}) = \mathbf{b}\cdot (\mathbf{c}\times\mathbf{a}) = \mathbf{c}\cdot (\mathbf{a}\times\mathbf{b}) = \mathbf{0}.
Last reply 5 hours ago
Edexcel A Level Mathematics Paper 1 (9MA0 01) - 4th June 2024 [Exam Chat]Last reply 5 days ago
Edexcel IGCSE Higher tier Mathematics A Paper 1 1H (4MA1) - 8th November 2023Last reply 1 month ago
Edexcel GCSE Mathematics Paper 3 (1MA1 3) - 13th November 2023 [Exam Chat]Last reply 1 month ago
Edexcel GCSE Statistics Paper 1 Higher Tier (1ST0 1H) - 12th June 2023 [Exam Chat]284
Last reply 1 month ago
Edexcel A Level Mathematics Paper 1 (9MA0 01) - 6th June 2023 [Exam Chat]2960
Last reply 1 month ago
AQA A Level Mathematics Paper 1 (7357/1) - 6th June 2023 [Exam Chat]352
Last reply 1 month ago
Edexcel GCSE Mathematics Paper 2 (1MA1 2) - 10th November 2023 [Exam Chat]Last reply 2 months ago
Edexcel A-level Mathematics Paper 1 [6th June 2023] Unofficial Markscheme156
Last reply 2 months ago
Edexcel GCSE Mathematics Paper 1 (1MA1 1) - 8th November 2023 [Exam Chat]Last reply 3 months ago
Edexcel IGCSE Higher tier Mathematics A Paper 1 1H (4MA1) - 19th May 2023 [Exam Chat]232
Last reply 3 months ago
AQA GCSE Mathematics Paper 3 (Higher) 8300/3H - 14th June 2023 [ Exam Chat]247
Last reply 5 months ago
Edexcel IGCSE Higher tier Mathematics A Paper 2 2H (4MA1) - 10th November 2023Last reply 7 months ago
OCR A-level Mathematics A Paper 3 (H240/03) - 20th June 2023 [Exam Chat]169
Last reply 8 months ago
AQA Level 2 Further Maths 2023 Paper 1 (8365/1) & Paper 2 (8365/2) [Exam Chat]489
Last reply 8 months ago
Edexcel A Level Mathematics Paper 3 (9MA0 03) - 20th June 2023 [Exam Chat]1836
Last reply 8 months ago
AQA A Level Mathematics Paper 3 (7357/3) - 20th June 2023 [Exam Chat]307
Last reply 8 months ago
OCR A-level Mathematics B Paper 3 (H640/03) - 20th June 2023 [Exam Chat]132
Last reply 9 months ago
Edexcel A-level Further Mathematics Paper 1 (9FM0 01) - 25th May 2023 [Exam Chat]902
Last reply 5 hours ago
Edexcel A Level Mathematics Paper 1 (9MA0 01) - 4th June 2024 [Exam Chat]Last reply 5 days ago
Edexcel IGCSE Higher tier Mathematics A Paper 1 1H (4MA1) - 8th November 2023Last reply 1 month ago
Edexcel GCSE Mathematics Paper 3 (1MA1 3) - 13th November 2023 [Exam Chat]Last reply 1 month ago
Edexcel GCSE Statistics Paper 1 Higher Tier (1ST0 1H) - 12th June 2023 [Exam Chat]284
Last reply 1 month ago
Edexcel A Level Mathematics Paper 1 (9MA0 01) - 6th June 2023 [Exam Chat]2960
Last reply 1 month ago
AQA A Level Mathematics Paper 1 (7357/1) - 6th June 2023 [Exam Chat]352
Last reply 1 month ago
Edexcel GCSE Mathematics Paper 2 (1MA1 2) - 10th November 2023 [Exam Chat]Last reply 2 months ago
Edexcel A-level Mathematics Paper 1 [6th June 2023] Unofficial Markscheme156
Last reply 2 months ago
Edexcel GCSE Mathematics Paper 1 (1MA1 1) - 8th November 2023 [Exam Chat]Last reply 3 months ago
Edexcel IGCSE Higher tier Mathematics A Paper 1 1H (4MA1) - 19th May 2023 [Exam Chat]232
Last reply 3 months ago
AQA GCSE Mathematics Paper 3 (Higher) 8300/3H - 14th June 2023 [ Exam Chat]247
Last reply 5 months ago
Edexcel IGCSE Higher tier Mathematics A Paper 2 2H (4MA1) - 10th November 2023Last reply 7 months ago
OCR A-level Mathematics A Paper 3 (H240/03) - 20th June 2023 [Exam Chat]169
Last reply 8 months ago
AQA Level 2 Further Maths 2023 Paper 1 (8365/1) & Paper 2 (8365/2) [Exam Chat]489
Last reply 8 months ago
Edexcel A Level Mathematics Paper 3 (9MA0 03) - 20th June 2023 [Exam Chat]1836
Last reply 8 months ago
AQA A Level Mathematics Paper 3 (7357/3) - 20th June 2023 [Exam Chat]307
Last reply 8 months ago
OCR A-level Mathematics B Paper 3 (H640/03) - 20th June 2023 [Exam Chat]132
Last reply 9 months ago
Edexcel A-level Further Mathematics Paper 1 (9FM0 01) - 25th May 2023 [Exam Chat]902