I have no idea where to start to prove this.

Let where is the identity, is a non-zero row vector in and denotes transpose of . If is symmetric, show that .

both symmetric, then of course is symmetrc. But how to show is equal to identity?

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- March 30th 2010, 02:30 AMdeniselim17linear algebra proof
I have no idea where to start to prove this.

Let where is the identity, is a non-zero row vector in and denotes transpose of . If is symmetric, show that .

both symmetric, then of course is symmetrc. But how to show is equal to identity? - March 30th 2010, 05:40 AMtonio

Without any further conditions this is false: take for example , then:

, so is symmetric but is not the unit matrix.

As you say: sum/difference and product of symmetric matrices is symmetric, so the above difference will**always**be a symmetric matrix, no matter what is.

Tonio - March 30th 2010, 06:47 PMdeniselim17
- March 30th 2010, 07:52 PMtonio