How Do You Find the First Time Position and Velocity Reach Their Maximum Values?

[lefthand]

this here is the problem...

Use the equations below. (Note that the direction is indicated by the sign in front of the equations.)
x = (0.0553 m) cos(4.094t + 0.14π)

v = −(0.226 m/s) sin(4.094t + 0.14π)

a = −(0.927 m/s2) cos(4.094t + 0.14π)

(a) Determine the first time (t > 0) that the position is at its maximum (positive) value.
s

(b) Determine the first time (t > 0) that the velocity is at its maximum (positive) value.
s

i have no idea where to start, or how to do this.

 

[grzz]

Position is given by x.

At what angle is the cos(...) maximum?

 

[lefthand]

they didnt give an angle. but I'm guessing since we want x to equal what ever number is there, then cos must equal 1 right?

 

[grzz]

so (0.0553 m) cos(4.094t + 0.14π) is max when cos(4.094t + 0.14π) = 1

that is when (4.094t + 0.14π) = ...?