# Pythagorean Theorem proof Vector Calc. Due tomorrow 9am. PLEASE HELP

1. Sep 3, 2008

### rgalvan2

Pythagorean Theorem proof Vector Calc. Due tomorrow 9am. PLEASE HELP!!

Prove the Pythagorean theorem. That is, if a,b, and c are vectors in Rn such that a + b = c and a.b = 0, then ||a||2 + ||b||2 = ||c||2. Why is this called the Pythagorean theorem.

Hint given: Given the hypotheses, you have a right triangle. Why?

Help please! This is due tomorrow morning and I cannot figure it out.

||x||= length of variable
a.b= dot product

2. Sep 3, 2008

### Hitman2-2

Re: Pythagorean Theorem proof Vector Calc. Due tomorrow 9am. PLEASE HELP!!

Well what does $$a \cdot b = 0$$ tell you about the vectors a and b?

3. Sep 3, 2008

### rock.freak667

Re: Pythagorean Theorem proof Vector Calc. Due tomorrow 9am. PLEASE HELP!!

Draw a triangle,explain why the angle is 90 degrees and then think cosine rule.