# Why does this always equal $1$?

One of my friends told me this. Take a calculator and continuously input $\cos\tan\sin\cos\tan\sin\ldots$ any number of times you want and finally in the place of the angle measure place any value of your choice (ANY). The result the calculator told me 99 out of 100 times was 1. And the one time it didn't tell me 1, it told me 0.9999999. Why does this happen?

• Nice!!! To make it easier on readers who are using Windows calculator, you should give the instructions "in reverse": Input any value you like, then click sin, then click tan, then click cos. +1. – barak manos Mar 5 '15 at 18:54
• The answer is pretty obvious, BTW. Sin brings it to a value between $-1$ and $1$. Tan therefore brings it to a value close to $0$, and Cos therefore brings it to a value close to $1$. – barak manos Mar 5 '15 at 18:55
• It apparently only works in degrees. – Matt Samuel Mar 5 '15 at 18:57