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At Right Angles November 2019

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AtRiA, November 2019 focuses on journeys -some are enjoyable, some tiresome, some endless. A mathematician’s journey is full of unexpected delight, simply because of unexpected detours, sudden discoveries and interesting alternatives. Have fun as you travel with us. Read all about the young Yatris and their journey of discovery in Features. This section also describes more abstract journeys from the Regular Pentagon to the Icosahedron and the Dodecahedron (Part 2) and from the familiar 2 and 3 dimensions to n dimensions in Extension of the Pythagorean Theorem. In ClassRoom, Simple Cryptography and Triangles with Integer Sides are articles sparked off by previous articles in AtRiA . An Unusual Proof of the Centroid Theorem, Modified Pascal Triangle and Orthocentre of a Triangle may motivate you to write similarly! You will find ideas in our regular columns – How to Prove It, Low Flow High Ceiling and TechSpace which features the simulation of a dice game this time. Our issue is short of 100% without the PullOut, enjoy the learning trajectory on Percentages, defined and illustrated with plenty of examples in this issue. How Craig Barton Wishes he’d Taught Maths is an excellent review by Sir Timothy William Gowers, reprinted from his Weblog. If not yet subscribed for hard copy send in your brief profile and postal address to [email protected] and do share your feedback at [email protected]


Sneha Titus






Vinay Nair
A Mathematical Pilgrimage: Ramanujan Yatra

Laxman N. Katkar
Extensions of the Theorem of Pythagoras


Shashidhar Jagadeeshan
From Regular Pentagons to the Icosahedron and Dodecahedron via the Golden Ratio – II



M Narasimha Murthy
Brahmagupta’s Theorem

Megharaj Bhatt
Simple Cryptography


A. Ramachandran
Generalising the Divisibility Tests of 9 and 11

Rajatadri Venkatasubban
An Unusual Proof of the Centroid Theorem


Anand Prakash
A Modified Pascal Triangle

Shreyan Jha
Explorations on Triangles with Integer Sides


Swati Sircar
TearOut Isometric Sketches and More

Swati Sircar
Low Floor High Ceiling Tasks In-cyclic Quads


Shailesh Shirali
How to Prove it

Avipsha Nandi
Orthocentre of a Triangle and its Distance from any Point in the Plane


Tech Space

Jonaki B Ghosh
The Game of Craps


Problem Corner

A Ramachandran
Middle School Problems on Averages

Prithwijit De & Shailesh Shirali
Problems for the Senior School


Jaleel Radhu
A Challenging Geometric Construction Problem



Sir William Timothy Gowers
How Craig Barton Wishes he’d Taught Maths


PadmaPriya Shirali


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