given that

f(t) =

cost, t < pi

0, t >= pi (>= is my notation for greater than or equal to)

Is the the correct way to write the above in heaviside notation:

f(t) = cost + u_pi_(t)(-cost)

Thanks. Also, does any know of any good resources out there that explain heaviside/step functions? Ive used Pauls Online notes and some youtube videos, just wondering if there are other suggestions out there.