A transverse harmonic wave on a string

 A transverse harmonic wave on a string is described by y (x,t) = 3.0 sin (36t + 0.018x + π/4) where x and y are in cm and t is in s. The positive direction of x is from left to right

(a) the wave is travelling from right to left

(b) the speed of the wave is 20 m/s

(c) frequency of the wave is 5.7 Hz

(d) the least distance between two successive crests in the wave is 2.5 cm