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mr_coffee

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This one is probably really simple, i don't understand how i'm suppose to write it.

4. Write each combination of vectors as a single vectory.

(c) QS - PS; (d) RS + SP + PQ; //i can't draw vector notation, but there should be an arrow on top of each group of letters, like QS.

31. A woman walksdue west on the deck of a ship at 3 mi/h. The ship is moving north at a speed of 22 mi/h. Find the speed and direction of the woman reltive to the surface of the water. I found the speed by just using sqrt(3^2 + 22^2) = 22.2 mi/h. But i'm confused on how i'm suppose to find the direction. THe book has an answer of: North 8 degrees West.

34. The tension T at each end of the chain has a magnitude 25N. What is the weight of the chain. The picture looks like it has a triangle on each side of the bank, forming a 37 degree angle. The trinagle is tension of course. So i figured the X compoents would cross out and u'd be left with the Y compoents in the +Y direction, so i just added those 2 vectors up and got 30 lb, does that sound like the right procedure?

40. If r = <x,y>, r1 = <x1,y1>, and r2 = <x2,y2>, describe the set of all points (x,y) such that |r - r1| + |r - r2| = k, where k > |r1-r2|

I'm completely lost on this one.

43. Use vectors to prove that the line joining the midpoints of two sides of a traingle is parallel to the third side and half its length. I'm also confused on how to do this one.

Thanks!