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# What are the magnitude and direction?

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## What are the magnitude and direction?

If a = (5, -12), what are the magnitude and direction of a?

The above question marked me wrong I answered:
(13, 292.6°)

I double checked this online and my answer was correct

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Originally Posted by csabin
If a = (5, -12), what are the magnitude and direction of a?

The above question marked me wrong I answered:
(13, 292.6°)

I double checked this online and my answer was correct
I calculated (13, 337deg). Here is what I have for the angle...270deg + 67deg = 337deg.

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Originally Posted by Uguessus
I calculated (13, 337deg). Here is what I have for the angle...270deg + 67deg = 337deg.

I even went back to a calculator website. The angle should be 360-67.3 = 292.7 degrees because if you think of this even logically the vector would have to be closer to the y axis much closer to 270 degrees. Due to the fact that -12 is much larger then 5.

Also you can even prove this with a calculation arctan(-12/5) = -67.3 degrees. I’m 1000% positive this is an error on test guide or I have wrote the problem wrong.

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You are right. I made a big mistake on where I should add or deduct the 67deg, 292Deg is right.

5. Originally Posted by Uguessus
You are right. I made a big mistake on where I should add or deduct the 67deg, 292Deg is right.
Always make a visual verification that you are in the right quadrant using the (X,Y) as a basis for your final answer.

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Originally Posted by Kalbi_Rob
Always make a visual verification that you are in the right quadrant using the (X,Y) as a basis for your final answer.
That's a good point. Thanks.

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## Update Question Please

Any way the moderators may be able to update this question to the correct answer? I also got it marked wrong, and came up with the same answer deemed correct in this forum topic.

8. Originally Posted by bob152637485
Any way the moderators may be able to update this question to the correct answer? I also got it marked wrong, and came up with the same answer deemed correct in this forum topic.
Thanks for reporting, someone will take a look.