Consider an equilateral triangle having vertices at the points A(2√3eiπ/2),B(2√3e−iπ/6),C(2√3e−i5π/6) Let P be any point on its incircle. then AP2+BP2+CP2=
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Solution
Let, z1=2√3eiπ/2,z2=2√3e−iπ/6,z3=2√3e−i5π/6 Clearly, the points lie on the circle |z|=2√3 and △ABC is equilateral triangle. Here, z1+z2+z3=0⇒¯¯¯¯¯z1+¯¯¯¯¯z2+¯¯¯¯¯z3=0 Since triangle is equilateral, inradius r=OD=1√3 unit Let P(z) be any point on the incircle, Now, AP2=|z−z1|2=|z|2+|z1|2−(z¯¯¯¯¯z1+¯¯¯zz1) Similarly, BP2=|z|2+|z2|2−(z¯¯¯¯¯z2+¯¯¯zz2) CP2=|z|2+|z3|2−(z¯¯¯¯¯z3+¯¯¯zz3)