## Triangle

A triangle is a closed shape having three sides; understanding its geometry is an interesting ride. Geometry differentiates similarity and congruency. Congruency implies similarity, but the converse violates validity. Similarity of triangles is based on two aspects, their corresponding angles and sides proportionate. About isosceles triangle, Thales gave some interesting results. The basic proportionality theorem of Thales solved many such occult. If in two triangles the corresponding angles are equal, then their corresponding sides are proportional. Estimating proportionality of sides is a practical activity; doing this for similar triangles boosts numerical accuracy. If all sides of a triangle are proportional to another triangle, then they are similar with equal corresponding angles. If a pair of angles of a triangle is equal to a pair of angles of another triangle, it is enough for similarity that the sides including these angles are proportional. Using similarity concepts, we can prove Pythagoras's theorem. Examining the relation of area and sides of similar triangles is a useful decorum.

## Outlier

Pesky data points that obstruct results. occurring far away from others. Wishing to delete them, but never should, if correct.

**Shashi Kant Pandey**, shashikantshvet@gmail.com, is an assistant professor in the Department of Computer Science at Maharaja Surajmal Institute in Janakpuri, New Delhi.

**Jacqueline Shaffer** is a statistical consultant living in California.