Dears,

I need the solution of the following exercise:

Let V be a real vector space and E an idempotent linear operator on V, i.e.,

a projection. Prove that (I + E) is invertible. Find (I + E)^{-1}. (where I is the identity operator)

Best Regards

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- May 20th 2012, 03:19 AMraedquestion about projection
Dears,

I need the solution of the following exercise:

Let V be a real vector space and E an idempotent linear operator on V, i.e.,

a projection. Prove that (I + E) is invertible. Find (I + E)^{-1}. (where I is the identity operator)

Best Regards - May 21st 2012, 03:03 AMDevenoRe: question about projection
hint:

suppose A is a matrix such that (I + E)A = I.

then A + EA = I.

applying E to both sides we have:

E(A + EA) = E

EA + E^{2}A = E

but E^{2}= E (since E is a projection) thus:

2EA = E, or EA = (1/2)E.

now substitute this back in the equation

A + EA = I, and solve for A.