What is a Matrix?

In mathematics, a matrix (plural matrices) is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns.

What is a Tangent Line?

A tangent line a line that touches a curve at a point without crossing over. Formally, it is a line which intersects a differentiable curve at a point where the slope of the curve equals the slope of the line.

source: http://www.mathwords.com/t/tangent_line.htm

History of Linear Equations?

The person who invented linear equations is William Rowan Hamilton. He introduced linear equations in 1843. These equations describe mechanics in three dimensional space and are an important historical discovery.