Equation of circle passes through (3,5),(5,5) and (3,−3) is Let equation be x2+y2+2gx+2fy+c=0 This is passes through (3,5),(5,5) and (3,−3) 6g+10f+c=−34 10g+10f+c=50 6g−6f+c=−18 From Eqs. (i), (ii) and (iii) g=−4, f=−1‌ and ‌c=0 Required equation of circle x2+y2−8x−2y=0 and given circle is x2+y2+2x+2fy=0 are orthogonal 2(−4)(1)+2(−1)f‌=0+0 f‌=−4