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## Homework Statement

Two points on a string are observed as a traveling wave passes. The points are at

*x*1 = 0 and

*x*2 = 1 m. The two points are known to be less than one wavelength apart. The transverse motions of the two points are observed to be

y

_{1}=0.2 sin 3πt

y

_{2}=0.2 sin (3πt+π/8)

**(a)**What is the frequency of this wave in hertz?

**(b)**What is the wavelength?

**(c)**What is the wave speed?

**(d)**Can you tell if this wave is moving to the right or to the left? If so, which way is it moving?

**The attempt at a solution**

For part (a), I simply found the frequency by knowing that ω=3π and ω =2πf.

However, for part (b), I could not find the text's book answer by just using k=2π/λ

the answer's from text book for b is

Any good explanations or hints for me? I have been reading the textbook again and again, but still can't find why.

(textbook = AP FENCH, vibrations and wave)