Ship moving at constant velocity between two radar positions

[Loppyfoot]

Homework Statement

A stationary radar operator determines that a ship is 12 km south of him. An hour later the same ship is 10 km southeast. If the ship moved at constant speed and always in the same direction, what was its velocity during this time?

This is so easy but I am just so confused about how to solve it.

 

[mgb_phys]

Draw a diagram.
Find the two points and draw a line joining them - from the triangle you can find the length of the line (it's even a right angle to make it easier!)

 

[Loppyfoot]

I drew the diagram, but I couldn't find a right angle anywhere. Where is this right angle? I need to find the i and j unit vectors, but how?

 

[mgb_phys]

There is a line from the ship due south (ie down the page)
Then a line from the ship southeast ( 45deg down-left)
Then you have a line joining them - that's the path of the ship - you just need to find the length of this line

 

[Loppyfoot]

How would I find this in i and j vectors?