Let k be a positive real number. The line x+y = k and the circle x^2+y^2=k are drawn. Find k so that the line is tangent to the circle.
By symmetry, the line and the circle are tangent when k = 1.
That is incorrect, when k=1, the line and circle intersect meaning the line is NOT tangent to the circle.
The line and circle are tangent when k= 2.
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