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To prove:

and

Assuming:

A (x₁, y₁) and B (x₂, y₂) be the given points and O be the origin.

Explanation:

Slope of OA = m₁ = y_1x1

Slope of OB = m₂ = y_2x2

It is given that θ is the angle between lines OA and OB.

∴

⇒

Now,

As we know that

∴

⇒

⇒

Hence proved.