On Thu, 06 Mar 2008 14:29:25 -0600
Cecil Moore wrote:

Roger Sparks wrote:
So the question is "When does (x + y)^2 = x^2 + y^2 ?".

(x + y)^2 = X^2 + 2xy + y^2

X^2 + 2xy + y^2 = x^2 + y^2 only when either x or y = zero.

That's some "Food for Thought", Roger, but unfortunately
phasor math is more complex :-) than that. The "Rest of
the Story" is if x and y are phasors that are 90 degrees
out of phase with each other, is there another solution
besides the one you offered?

Given two phasors, 1v at 0 degrees and 1v at 90 degrees,
what is the sum of the square of the voltages vs the
square of the sum of the voltages. Hint: the phasor sum
of the voltages is 1.414.
--
73, Cecil http://www.w5dxp.com

OK, The vector sum is sqrt(1^2 + 1^2) = sqrt(2) = 1.414

I would think of the "square of the sum of the voltages" to be (1 + 1)^2 = 2^2 = 4

We must be very careful to not use scaler math when vectors are called for.

--
73, Roger, W7WKB