Vastaus:
#v (pi / 2) = - sqrt2 #
Selitys:
#if p = f (t);
# v = d / (d t) f (t) #
# v = d / (dt) (sin (2t-pi / 4) +2) #
#v (t) = 2 * cos (2t-pi / 4) #
# "for:" t = pi / 2 #
#v (pi / 2) = 2 * cos (2 * pi / 2-pi / 4) #
#v (pi / 2) = 2 * cos (pi-pi / 4) #
#v (pi / 2) = 2 * cos ((3pi) / 4) #
#cos ((3pi) / 4) = - cos (pi / 4) = - sqrt2 / 2 #
#v (pi / 2) = - 2 * sqrt2 / 2 #
#v (pi / 2) = - sqrt2 #