Question

How solve this equation where 0.8=0.2 cos (31.4 t) where 31.4 is the unit in radian per second and we want to find t (time)value, the answer is t=0.037 seconds, how to solve it algebraically?

Answer 1

Hi Shafiyah, you cannot really solve this equation because your function goes only from `0.2` to `-0.2` (amplitude) and `0.8` cannot be reached!

Explanation:

If you have `0.8` you have:
`0.8=0.2cos(31.4t)`
`cos(31.4t)=0.8/0.2=4` that cannot be (`cos` goes from `1` to `-1` only!);

If it is: `0.08=0.2cos(31.4t)` then:
`cos(31.4t)=0.08/0.2=0.4`
`31.4t=arcos(0.4)=1.1593`
`t=1.1593/31.4=0.037s`