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# c4 vectors watch

1. i bet this is a relli easy question but the book doesnt quite tell me how to do it.

The vector p has magnitude 10 units and is inclined at 150 degrees to the x-axis. Express p as a column vector.

i no that the values are 5 root3 and 5, but i dont no which is negative and positive.

help???
2. Draw a diagram. It's inclined at 150 degrees (anticlockwise) to the (positive) x-axis. Which quadrant of your graph is it in?
3. i think its in the second quadrant (without drawing)? does that tell u which bit is negative n positive?
4. (Original post by blacklashes)
i think its in the second quadrant (without drawing)? does that tell u which bit is negative n positive?
Yes.

cos describes x and sin describes y, hence in the second quadrant you are above the x axis, hence cos is positive and you are to the left of the y axis, hence sin is negative. Sorry for the crap explanation
5. (Original post by blacklashes)
i think its in the second quadrant (without drawing)? does that tell u which bit is negative n positive?
Well... yes. Draw the vectors (5 root 3, 5), (-5 root 3, 5), (5 root 3, -5), (-5 root 3, -5), and you'll see which one it is.
6. thanks it alls cleared up now!!! +
7. im not sure how to do this question...

Given that the points A and B are (3,5) and (1,10) respectively, find a vector equation for the line through the point A and perpendicular to B.
8. (Original post by blacklashes)
im not sure how to do this question...

Given that the points A and B are (3,5) and (1,10) respectively, find a vector equation for the line through the point A and perpendicular to B.
Perpendicular to a point?

Surely this isn't the correct question :P
9. (Original post by coffeym)
Perpendicular to a point?

Surely this isn't the correct question :P
I assume it means perpendicular to the line AB.
10. Could mean perpendicular to b.

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