{"id":11556,"date":"2022-07-18T14:48:11","date_gmt":"2022-07-18T09:18:11","guid":{"rendered":"https:\/\/mathemerize.com\/?p=11556"},"modified":"2022-07-18T14:48:14","modified_gmt":"2022-07-18T09:18:14","slug":"prove-that-the-sum-of-the-squares-of-the-diagonals-of-a-parallelogram-is-equal-to-the-sum-of-the-squares-of-its-sides","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/prove-that-the-sum-of-the-squares-of-the-diagonals-of-a-parallelogram-is-equal-to-the-sum-of-the-squares-of-its-sides\/","title":{"rendered":"Prove that the sum of the squares of the diagonals of a parallelogram is equal to the sum of the squares of its sides."},"content":{"rendered":"
We know that AD is a median of triangle ABC, then<\/p>\n
\\({AB}^2\\) + \\({AC}^2\\) = 2\\({AD}^2\\) + \\({1\\over 2}{BC}^2\\)<\/p>\n
Since the diagonals of a parallelogram bisect each other, therefore BO and DO are medians of triangles ABC and ADC respectively.<\/p>\n
\\(\\therefore\\)\u00a0 \\({AB}^2\\) + \\({BC}^2\\) = 2\\({BO}^2\\) + \\({1\\over 2}{AC}^2\\)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0………..(1)<\/p>\n
and\u00a0 \u00a0 \u00a0 \\({AD}^2\\) + \\({CD}^2\\) = 2\\({DO}^2\\) + \\({1\\over 2}{AC}^2\\)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 …………(2)<\/p>\n
Adding (1) and (2), we get<\/p>\n
\\({AB}^2\\) + \\({BC}^2\\) + \\({AD}^2\\) + \\({CD}^2\\) = 2(\\({BO}^2\\) + \\({DO}^2\\)) + \\({AC}^2\\)<\/p>\n
\\(\\implies\\)\u00a0 \\({AB}^2\\) + \\({BC}^2\\) + \\({AD}^2\\) + \\({CD}^2\\) = 2(\\({1\\over 4}{BD}^2\\) + \\({1\\over 4}{BD}^2\\)) + \\({AC}^2\\)<\/p>\n
\\(\\implies\\)\u00a0 \u00a0\\({AB}^2\\) + \\({BC}^2\\) + \\({AD}^2\\) + \\({CD}^2\\) = \\({AC}^2\\) + \\({BD}^2\\)<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":" Solution : We know that AD is a median of triangle ABC, then \\({AB}^2\\) + \\({AC}^2\\) = 2\\({AD}^2\\) + \\({1\\over 2}{BC}^2\\) Since the diagonals of a parallelogram bisect each other, therefore BO and DO are medians of triangles ABC and ADC respectively. \\(\\therefore\\)\u00a0 \\({AB}^2\\) + \\({BC}^2\\) = 2\\({BO}^2\\) + \\({1\\over 2}{AC}^2\\)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 …<\/p>\n