# Class 9-10

## Addendum to Theorem concerning A Magic Triangle

In the July 2018 issue of At Right Angles, the topic of magic triangles was explored, a ‘magic triangle’ being “an arrangements of the integers from 1 to n on the sides of a triangle with the same number of integers on each side so that the sum of integers on each side is a constant, the 'magic sum' of the triangle. There was some error in the proof and here in this article we will track down the error.

## Cutting a Square into Equal Parts

The article talks about a simple activity which can be performed with students of primary, middle and high school. The shape that is used to discuss here is a square and hence it is expected that students know the basic properties of a square. The article also talks about using lines. Even if students don't have a Euclidean notion of definition of a line, that idea can be instilled as the teacher executes this activity.

he Hill Cipher method in cryptography has been described in detail in earlier issues of At Right Angles [1] [2]. Through those articles, the reader will be familiar with the art of encryption and decryption of messages using matrices and modular arithmetic.

## W.W. Sawyer The Universal Math Teacher

As a corollary of Section 8 of the Right to Education Act, every young Indian citizen in elementary school today has the legal right to get mathematics education of good quality. Perhaps India is the only country in the world, where this is legally mandatory. Two questions are now squarely on the agenda of Indian math education: “What is math education of good quality?” and, “Is it possible to ensure this for every child?”

## The Constants of Mathematics – Part III

In this article, which is the third of our series on mathematical constants, we continue our exploration of Euler’s constant e. (Yes, we have had to devote more than one ‘episode’ to e, as there is so much to say about this number.)

## LATTICE POINT GEOMETRY

In this article, Shailesh Shirali begins with a seemingly simple question but develops the answer into not one, but four different proofs! While the content focuses on mathematics that has many applications, some of which are mentioned here, the multiplicity of proofs is an added draw, helping the teacher to illustrate innovative ways of thinking and connections across approaches.

## Climate of India

India is home to an extraordinary variety of climatic regions, ranging from tropical in the south to temperate in the Himalayan north, where elevated regions receive sustained winter snowfall. The nation's climate is strongly influenced by the Himalayas and The Thar Desert.Though the Tropic of Cancer—the boundary between the tropics and subtropics—passes through the middle of India, the bulk of the country can be regarded as climatically tropical.

## What is a Black Hole

Black Holes (BHs) are the standard-bearers of cool Physics. Pop culture is full of references to these objects that are so powerful that nothing can escape them. A lot of Physicists have spent their lives thinking about how BHs are formed, how they can be detected and what happens to objects that enter a BH.

## Walking Cylinder

This Walking Cylinder is made from a toilet roll, straws and other odd materials.

## Teaching Sustainable Development Goals in the Classroom

This lesson plan is about taking United Nation's Sustainable Development Goals in the classroom. This will foster the essence of global citizenship in the young minds, starting early from the school.

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