Graphing calculators are good, but the Graphing Calculator app by Desmos is better. Graphing calculators are expensive. *(The Desmos app is free).* Graphing calculators require several clicks to change the ‘window’ of a graph. *(The Desmos app is interactive and I can zoom in with my fingers). Graphing calculators can be finicky when entering complicated equations. **(The Desmos app points out your error). *

I could go on an on about why I think Desmos makes a better graphing calculator for my students, but instead I’ll tell you about my Trigonometry students.

We are headed towards proving trigonometric identities, but before start simplifying them by had, I had them graph pairs of equations whose **equations looked very different **but** graphs were identical**.

Two equivalent equations graphed at the same time.

Imagine their surprise when only one graph showed up! Several were concerned that they had done something wrong, but au contraire, they are equivalent equations! We had a lot of fun entering pairs of equations and deciding whether or not they were equivalent.

My students have started calling these trigonometric identities “same, same, but different” because they look the same on the graph, but they have different forms when written.

When I did this same activity last year with graphing calculators, it took forever to enter the equations and then find their mistakes if they forgot parentheses. **The Desmos app saved us a lot of time** and therefore allowed us to try lots of different pairs of equations.

Entering complicated equations is easy with this list of functions.

You can change the x- and y-axis to radians too!

Desmos also has a web based calculator that is just as fun!

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*Related*

Wouldn’t a link to this Desmos app be handy?

Great idea! Margaret added one above.

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