c=a×b=i^21j^11k^−20=2i^−2j^+k^
∣c∣=4+4+1=3, ∣a∣=4+1+4=3
From ∣c×d∣=3 and cos(∠(c,d))=21:
∣c∣∣d∣sin4π=3 → 3∣d∣⋅21=3 → ∣d∣=2
From ∣d−a∣2=11:
∣d∣2−2a⋅d+∣a∣2=11
2−2a⋅d+9=11
a⋅d=0
Let a=2i^+j^−2k^,b=i^+j^ and c=a×b. Let d be a vector such that ∣d−a∣=11,∣c×d∣=3 and the angle between c and d is 4π. Then a⋅d is equal to
Held on 24 Jan 2026 · Verified 6 Jul 2026.
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