Fantastic Mathematical Error

Maths can be taxing and stressful when dealing it in the "unknown" zone.

It causes anxiety. It causes sleepless nights. It makes one lost confidence.

Must it, however, end in this way?

No, looking at the mistakes made can sometimes make one laugh out loud and learn something out of it.

Example:

cos 2A = 0.5

Working:
cos A = 0.5 / 2

The above is applying the concept of dividing both side by the same factor (or number).
a + b = c ===> ( a + b ) / d = c / d

So the working above is CORRECT.

Interesting, right?

What happened?

The working is theoretically wrong.

Why?

"cos" is not a factor to be multiplied to 2A. It is an operation done onto the angle "2A". It is a whole piece of information "cos 2A" and has to "stick" together.

Wonder what happens to the thinking.

Lots of interesting and fantastic maths errors occur everyday around the world.

They make learning maths exciting and stimulating.

Do you agree?