# A level maths QWatch

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#1
Find the direction of the vector 12i-5j. Answer is 337.38. I don’t get why u do 360-22.62. Thanks.
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3 weeks ago
#2
(Original post by Defence11)
Find the direction of the vector 12i-5j. Answer is 337.38. I don’t get why u do 360-22.62. Thanks.
The convention is to measure angles by starting by pointing from the origin along the positive x-axis, and then turning anticlockwise. So although the angle is 22.62 degrees below the x-axis (and could be expressed as -22.62 degrees), it can also be expressed in the way that you say.
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#3
(Original post by Pangol)
The convention is to measure angles by starting by pointing from the origin along the positive x-axis, and then turning anticlockwise. So although the angle is 22.62 degrees below the x-axis (and could be expressed as -22.62 degrees), it can also be expressed in the way that you say.
Why minus 360 tho. Why not minus 180?
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#4
Can u draw me a diagram
(Original post by Defence11)
Why minus 360 tho. Why not minus 180?
0
3 weeks ago
#5
(Original post by Defence11)
Can u draw me a diagram
Not a very good one, but OK... Theta is easily seen to be 22.62 degrees (4 s.f.), and alpha is the angle you want.
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