12.7 problem 3

Dear Professor Taylor,

I have tried many times on number 3. The the last
two are counting my second coordinate as wrong, even though I believe they
are correct.

My Cartesian coordinates are ((5/4)sqrt6, -(5/4)sqrt2,
-(5/2)sqrt2)

My answer is (5, -pi/6, 2.356)


 (-(5/4)sqrt6, -(5/4)sqrt2,
-(5/2)sqrt2)

My answer- (5, -2.6179938,2.256)

Thank you,
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The only problem that you are having here is that you are thinking of negative angles, while this webwork problem is set up to only consider positive angles measured counter-clockwise from the positive x-axis.