N. P. Bali, N. Ch. Narayana Iyengar - Engineering mathematics - 2004 - 1438 pages
...Prove that the altitudes of a triangle are concurrent. (Andhra, 1986 ; Raipur, 1986) 10. Prove that the median to the base of an isosceles triangle is perpendicular to the base. 11. Prove that the sum of the squares of the diagonals of a parallelogram is equal to the sum of the...
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