The position vectors of the points A, B, C, D are i+j+3k, 3i – j + 5k, i − j + k, 5i – 5j + αk, respectively, where α is a positive integer. It is given that the shortest distance between the line AB and the line CD is equal to 2√2.
- (i)Show that the possible values of α are 3 and 5.[7]
- (ii)Using α = 3, find the shortest distance of the point D from the line AC, giving your answer correct to 3 significant figures.[3]
- (iii)Using α = 3, find the acute angle between the planes ABC and ABD, giving your answer in degrees.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [B1]
- [M1A1]
- [M1A1]
- [A1]
- [A1] (AG)
- [B1]
- [M1A1] Use DP.AC = 0 to find λ (= -5/3) M1 Find length A1
- [A1]
- [B1B1]
- [M1A1]
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