I use `toRadians()` to convert value and find trigonometry such this

`dataMain = Math.cos(Math.toRadians(dataSub);`

but i have a problem such as `dataSub = 60` 

Answer should be `0.5` 
but answer in my program is `0.50000000000001`

Or even `dataSub = 30`

`dataMain = Math.sin(Math.toRadians(dataSub);`

answer in my program is `0.49999999999994`

How can i fix this problem?