תשובה:
#v (pi / 2) = - sqrt2 #
הסבר:
#if p = f (t); #
# v = d / (d t) f (t) #
# v = d / (d t) (חטא (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 #