Question 1072045
{{{cos^2(x)+sin^2(x)=1}}}
{{{cos^2(x)+144/169=1}}}
{{{cos(x)=-sqrt(1-144/169)}}}
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{{{cos(x)=sqrt(5)/2>1}}}
Check your setup for the second part.
The value of the cosine must be less than or equal to 1.