[WWfeedback]: Section_10.2 prob:10

Hi Dr. Taylor,
I'm having some trouble with the second part of this
question. I initially used the equation 5=sqrt(194)cos(a) to find a (the
angle). And when I did that, I got the answer of 1.2 rad, which came back
wrong. So, I tried subtracting 1.2 rad from pi/2 to get 0.37 rad, which
also came back wrong. It turns out you get the same answers using
tan^-1(a)=13/5, and u*v=|u||v|cosa, where u= (5, 13) and v=(0, 13). How
should I try to approach this problem?
Thank you,
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the only mistake you are making is that WebWork is expecting three decimal places of accuracy