Which of the following equations can form stationary waves

PHYSICS · Single correct · A Level · Physics · Waves · Waves

Problem

Which of the following equations can form stationary waves? (i)

y = A \sin (\omega t - kx)

(ii)

y = A \cos (\omega t - kx)

(iii)

y = A \sin (\omega t + kx)

(iv)

y = A \cos (\omega t + kx)

(1) (i) and (ii) (2) (i) and (iii) (3) (iii) and (iv) (4) (ii) and (iv)