New posts in Analytic Geometry

For $a$, $b$, $c$ the sides of a triangle, show $ 7(a+b+c)^3-9(a+b+c)\left(a^2+b^2+c^2\right)-108abc\ge0$

What is a generally accepted definition of "curve" in mathematics?

Why does the sign of this determinant change when changing the sense of vertices?

Find the line of intersection between two planes.

Find equation of the circle whose diameter is the common chord of two other circles?

A square inside an equilateral triangle

Visualize the proof of $\mathcal{H} = M \oplus M^{\perp}$, where $\mathcal{H}$ Hilbert space, $M$ closed subspace

Prove that $d$ passes through a fixed point.

Showing that the locus of point $N$ is $x^2+y^2=a^2$

Geometrical meaning of the formula for the area of a triangle using a $3\times3$ matrix.