29&30 sama caranya tolong banget ya..

a sin bx
melalui (0,3)
3 = a sin (b×0)
3 = a × 0
a = 0
y = 0 (tidak memenuhi)

melalui (0,3)
y = a cos bx
3 = a cos (b×0)
3 = a × 1
a = 3

y = 3 cos bx
melalui (90,-3)

-3 = 3 cos (b×90)
-1 = cos (b×90)
cos (90b) = -1
= cos 180
90b = 180
b = 2

jadinya,, x = 3 cos 2x


JADIKAN YG TERBAIK YAAAAAAAAAAA