- #1

adjacent

Gold Member

- 1,552

- 63

## Homework Statement

This is not a homework question,but I will post here anyway.

##\vec{AB}=\left(\begin{matrix} 1 \\ 2 \end{matrix}\right)##

##\vec{CD}=\left(\begin{matrix} 2 \\ 4 \end{matrix}\right)##

(a)Prove that ##|\vec{CD}|## is double of ##|\vec{AB}|##

(b)Prove that ##\vec{CD}## is parallel to ##\vec{AB}##

## The Attempt at a Solution

(a) The sides of right angle triangle are doubled here.

##c^2=b^2+a^2##

##2(a^2+b^2)=2c^2##

If a and b double,c will also double.

(b) ##\theta=\tan^{-1}\left(b \over a \right)##

##\theta=\tan^{-1}\left(\frac{b}{a} \right)##

Which means even if the two sides double,the angle will not double,therefore the slope of vector will not change.

I don't think this is a proof.Can anyone help me?

Also what are the uses of Vectors like this?( I just learned them today)

Last edited: