- #1
JG89
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Homework Statement
Let V be an inner product space. If <x,y> = <x,z> for all x in V, then prove that y = x.
Homework Equations
The Attempt at a Solution
Since V is a vector space, it follows that (y - z) is an element of V. Since <x,y> = <x,z> for ALL x, we put x = (y-z). Then we have <y - z, y> - <y - z, z> = 0. Since inner products are conjugate linear in the second component, we can write:
<y - z, y> - <y - z, z> = <y -z, y - z> = 0. I know that in general <w,w> = 0 if and only if w = 0. Thus we must have y - z = 0, implying that y = z.
Is this correct?