# Derivative of implicite function.

Submitted by Isoscel on Thu, 03/20/2008 - 07:34.Let consider the equation

We know that the set of solution of this equation is the set of points in plane at distance 1 from the origin, or a circle of radius 1 with center in (0,0).

We want to give a description of this set depending on a single variable instead of two.

This is possible only local ,not for the whole set of solutions.

But the collection of local solutions can give us a complete information about the circle.

Let with and

For in a small neighborhood of we have

# In a triangle the sum of the angles is 180

Submitted by Isoscel on Wed, 03/19/2008 - 00:45.In any triangle the sum the angles is 180.

In triangle ABC:

Proof

Let consider line DE by A parallel to BC

Then and but

.

# Definition of Angle

Submitted by Structure on Wed, 03/19/2008 - 00:39.An angle is formed by two rays that have a common origin.

Two intersecting lines form 4 angles. The opposing ones are congruent and the neighboring ones have the sum 180 (are supplementary angles).

AEC = DEB

AED = CEB

AEC + AED = 180

CEB + BED = 180

AEC + CEB = 180

DEA + BED = 180