Answers:
- Choice D
- Choice D
- Choice C
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Explanations:
Problem 1
A = (4,4)
B = (-12,8)
Vector u starts at A and ends at B. The arrow points to B.
Subtract x coordinates: xB - xA = -12-4 = -16
Subtract y coordinates: yB - yA = 8-4 = 4
The vector is u = <-16, 4> which is in quadrant Q2.
Use the pythagorean theorem to find the length of the vector.
a^2 + b^2 = c^2
c = sqrt( a^2 + b^2 )
||u|| = sqrt( (-16)^2 + 4^2 )
||u|| = 16.492
Now compute the angle
theta = arctan(b/a)
theta = arctan(4/(-16))
theta = -14.036
Add on 180 degrees so the angle lands in Q2.
-14.036+180 = 165.964
The angle is roughly theta = 165.964 degrees
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Problem 2
A = start point = (4, 3)
B = end point = (-4, -1)
Subtract x coordinates: xB - xA = -4 - 4 = -8
Subtract y coordinates: yB - yA = -1-3 = -4
v = <a, b> = <-8, -4> which is in Q3
Use the pythagorean theorem to find the length of the vector.
a^2 + b^2 = c^2
c = sqrt( a^2 + b^2 )
||v|| = sqrt( (-8)^2 + (-4)^2 )
||v|| = 8.944
And,
theta = arctan(b/a)
theta = arctan(-4/(-8))
theta = 26.565
We need to add on 180 so we move from Q1 to Q3
26.565+180 = 206.565
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Problem 3
The notation <-3, 4> means "move 3 units left, 4 units up".
Only vector r fits the description as we move from the initial point (5,3) to the terminal point (2,7)
