In any triangle, A+B+C = 180 degrees. How does dA + dB + dC = 0?

[Prateek]

When I was reading the illustrative examples of a chapter (using derivatives for measuring rates) from my calculus book, I found something like this in the middle of a sum:

A + B + C = Pi, therefore, dA + dB + dC = 0

I just want to know how does it come out. Can anyone please prove it?

 

[Karan]

Derivative of a constant = 0

 

[bdwolfhound]

Without seeing the rest of it one can only guess. However, here is a guess

(A + B + C) = (pi = 180°) = constant and therefore
d(A + B + C) = 0.....but
d(A + B + C) = dA + dB + dC
dA + dB + dC = 0

It is telling you that since the sum of the angles is constant, the sum of the changes in them must be zero.

 

[michael]

someone can just not me