If A 2 + B 2 represents the magnitude of resultant of two vectors A → + B → and A → - B → , then the angle between two vectors is

Question

If A 2 + B 2 represents the magnitude of resultant of two vectors A → + B → and A → - B → , then the angle between two vectors is, cos - 1 ⁡ - 2 A 2 - B 2 A 2 + B 2, cos - 1 ⁡ - A 2 - B 2 A 2 B 2, cos - 1 ⁡ - A 2 + B 2 2 A 2 - B 2, cos - 1 ⁡ - A 2 - B 2 A 2 + B 2

MARKS App · Accepted Answer

A 2 + B 2 = A + B 2 + A - B 2 + 2 A + B A - B . c o s θ ⇒ A 2 + B 2 = 2 A 2 + B 2 + 2 A 2 - B 2 . c o s θ ⇒ c o s θ = - A 2 + B 2 2 A 2 - B 2 ⇒ θ = c o s - 1 - A 2 + B 2 2 A 2 - B 2

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