Question 36646:  This is my second and last question. This is not in a textbook.
 
a.)Let T be a linear operator on V. SHow that if (Tu|v)=0 for every u,v in V, then T is the zero operator on V. 
b.)Prove the Generalized Pythagorean Theorem: Suppose {v1,v2,...,vn} is an orthogonal set of vectors.  Then ||v1+v2+...+vn||^2=||v1||^2+...||v2||^2+...+||vn||^2
 
For (a.) I think you fix u and get it, but I don't understand how. 
For (b.) Do I only have to do this: 
     ||v1+v2+...+vn||^2=(v2+v2+...vn|v1+v2+...+vn) 
                       =(v1|v1)+(v2|v2)+...(vn|vn) since the vectors are orthog. 
                       =||v1||^2+...||v2||^2+...+||vn||^2 
Is this all i have to do or is there more steps in there? 
 Answer by venugopalramana(3286)      (Show Source): 
You can  put this solution on YOUR website! YOU ARE INTERESTED IN SECOND BIT 
YOU BETTER WRITE CLEARLY THAT THE VECTORS BEING ORTOGONAL 
V1*VJ=0...IF I IS NOT EQUAL TO J AND  
VI*VJ=|VI|^2...IF I=J.....WHICH PROVES THE IDENTITY 
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