Answer: 225
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Step-by-step explanation:
Take note that the x and y coordinate of this vector are the same.
This leads to a 45-45-90 reference triangle. If the vector was in the first quadrant (the northeast), then the answer would be 45 degrees.
However, we need to add on 180 so we get to the third quadrant instead where x and y are both negative. This gets us to 180+45 = 225 degrees
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If you wanted to use a calculator, then you would compute the value of
where <a,b> is the vector in question.
Since a = b in this case, we have b/a = 1 and the arctangent of this is 45 degrees. The adjustment of adding on 180 still applies like from before.