ABC is an isosceles triangle inscribed in a circle of radius r. If AB=AC and h is altitude from A to BC, then limh→0△p3 is equal to (where △ is the area and P is the perimeter of the triangle ABC)
1/128r
∵ AD = h
∴ OD = (h-r)
Then, BC = 2DC = 2√r2−(h−r)2
∴ BC = 2√2hr−h2
△ = 12.BC.h = h√(2hr−h2)
= h3/2√(2r−h)
and AB = AC = √h2+(DC)2 = √h2+r2−(h−r)2
= √2hr
∴ P = AB + BC + CA
= 2√2hr+2√(2hr−h2)
= 2(h)1/2(√2r+√2r−h)
Then, limh→0△p3 = limh→0h3/2√(2r−h)8h3/2(√2r+√2r−h)3
= √2r8(2√2r)3 = 1128r