To calculate the amplitude ymax(x) of the resultant wave at x = 2.21 m from the two harmonic waves y1 = Asin(kx - wt) and y2 = Asin(kx + wt), one must first recognize that the resultant wave can be expressed as a combination of the two. The amplitude of the resultant wave can be derived using the formula A = |2Asinkx|, which accounts for the superposition of the two waves. Understanding the values of A, k, and w is crucial for applying this formula correctly. Many participants in the discussion express frustration with the teaching methods and the disconnect between the course material and homework assignments. Overall, clarity on the underlying physics principles and proper guidance is essential for solving such problems effectively.