In linear algebra, triangular matrices play a very important role.

He is good at solving problems of trigonometric functions.

Trigonometric functions are one of the basic concepts in mathematics.

There is a complex love triangle between them.

I go to the gym every day to build my muscles.

This river is three long.

He likes to take a walk in the park at dusk.

The Winter Triangle is shining in the night sky.

Finding the Summer Triangle is helpful for remembering constellations.

A lower triangular matrix is a matrix where all the elements below the main diagonal are zero.