Superposition of Two Waves on a String: Amplitude and Wavelength Calculation

[dlc_iii]

Homework Statement

The equations for two waves traveling along the same string are $$f_1(x,t)=a\sin(bx-qt)$$ and $$f_2(x,t)=a\sin(bx+qt+\frac{1}{3}\pi),$$ with $$a=3.00\times 10^{-2},b=4\pi m^{-1},$$ and $$q=500s^{-1}$$. (a) Calculate the amplitude and wavelength of the resultant displacement of the string at t=3.00s

Homework Equations

$$f(x,t)=f_1(x,t)+f_2(x,t)$$
$$\sin(\alpha)+\sin(\beta)=2\sin\frac{1}{2}(\alpha+\beta)\cos\frac{1}{2}(\alpha-\beta)$$
$$\cos(\alpha)=\cos(-\alpha)$$
$$\lambda=\frac{2\pi}{k}$$

The Attempt at a Solution

I'm pretty sure that neither of the two things they are asking for depend on time, but I don't see why they'd give me the time like that if they didn't depend on time. I would answer $$A=2a\sin(bx+\frac{\pi}{6})$$ through superposition and then trig identity simplification and $$\lambda=\frac{2\pi}{b}$$ just from the equation. Is this right?

 

[Orodruin]

They want the amplitude of the wave as a function of x. This will generally depend on time. For example, when the two waves interfere destructively, that amplitude is zero.