**How to tell if 2 vectors are //? **

It's easy if you're given a diagram. What if a diagram isn't provided? Then we need to look at **relationship** between the vectors.

As long as 2 vectors are expressed as **scalar multiple** of each other, the 2 vectors are //. What exactly do I mean? Look at the following example equations, they are examples of vectors // to each other.

This also means if you're able to establish such relationship between 2 vectors, you can prove that the vectors are // to each other.

Very often, question will ask you to explain why A, B and C lie on a straight line. (Look at Example 3)

The term to describe 3 points on the line is known as **Collinear**.

**3 Points to show Collinear**

**Establish a relationship**between the 2 vectors**Conclude**that the 2 vectors are**//**to each other**Common point**is present

We can even draw a diagram to represent the two vectors. Since the relationship between the 2 vectors has a **negative sign**, it means that vectors AB and AC are in **opposite** direction. Vector AC is also twice of vector AB.

Do you have other ways to prove 3 points are collinear? I would love to hear from you.

Do you know that if you are asked to prove 2 vectors are //? A similar approach can also be used.

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