See Fig. A(5, 0) and B(0, 7) are the extremities of the given diagonal. Therefore, the slope of the diagonal AB is −7/5. Hence, the slope of the other diagonal, say, CD is 5/7. Therefore
tan θ = 5/7
so that cos θ = 7/√74 and sinθ = 5/√74
The equation of the diagonal CD is
Since, γ = 7/√74 the other vertices of the diagonal are