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junior college 1 | H2 Maths
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junior college 1 chevron_right H2 Maths chevron_right Singapore

vectors

Date Posted: 9 months ago
Views: 167
EPQP
EPQP
9 months ago
(i)

Given the vectors are perpendicular
a.(2a + b) = 0
2a.a + a.b = 0
2(2)² + 2|b|cos(3π/4) = 0
|b| = 4√2

(ii)

Length of projection
|a.b|/|b| = 8/(4√2) = √2 units

(iii)

OP = 3/5 OB

Area of ΔAPB
= Area of ΔOAB - Area of ΔOAP
= 1/2 |a × b| - 1/2 |a × p|
= 1/2 |a × b| - 1/2 × 3/5 |a × b|
= 1/2 (1 - 3/5) |a × b|
= 1/5 (2)(4√2)sin(3π/4)
= 8/5 units²

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