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Question : 92 of 120
Marks:
+1,
-0
Solution:
Given,
|a|=1,|b|=3 and
|a−b|=√7 ⇒‌‌|a−b|2=(√7)2 ⇒|a|2+|b|2−2a⋅b=7 ⇒(1)2+(3)2−2a⋅b=7 ⇒2a⋅b=10−7 ⇒a⋅b=‌ ⇒‌‌|a||b|‌cos‌θ=‌ ⇒‌‌1×3×cos‌θ=‌ ⇒‌‌cos‌θ=‌ ⇒‌‌θ=‌
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