Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two displacements are and .
Work one axis at a time:
Subtraction is the same with minus signs. Then use the signs of the two parts to find which quarter the arrow points into.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Work part by part, then find the size and the quarter.
Step 1. The sum. . Its size is .
Step 2. Its direction. Both parts are negative, so it points down and to the left. The angle with the axis is , so from it is .
Step 3. The difference. . Its size is .
Step 4. Its direction. The part is positive and the part negative: down and to the right. The angle below is , so from it is .
Answer: (a) , of size , at . (b) , of size , at .
Check. and . They give back the parts.
Watch out. A calculator gives , which points the opposite way. Always place the angle by the signs.
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