An ellipse is the trajectory of a moving point P. The sum of the distances from the moving point P to the fixed points F 1 and F2 in a plane is equal to a constant (greater than |F 1F2|), and F1and F2 are called the two focuses of the ellipse. The mathematical expression is | pf1|+pf2 | = 2a (2a > | f1F2 |).
An ellipse is a conic curve, that is, the tangent of a cone to a plane.
Extended data
The area of an ellipse is πab. An ellipse can be regarded as the stretching of a circle in a certain direction, and its parameter equations are: x=acosθ, y=bsinθ.
The tangent of the standard ellipse at point (x0, y0) is: xx0/a? +yy0/b？ = 1。 The slope of the ellipse tangent is: -b? x0/a？ Y0 can be obtained by complicated algebraic calculation.
Circumference:
Ellipse circumference formula: L=T(r+R)
T is an elliptic coefficient, and the value of the coefficient T can be obtained by looking up the value of r/R; R is the short radius of the ellipse; R is the long radius of the ellipse.
Ellipse circumference's Theorem: The circumference of an ellipse is equal to the product of the sum of the short radius and the long radius of an ellipse and the ellipse coefficient (including the perfect circle).
References:
Baidu encyclopedia-ellipse