Obtain the best least-square approximation to the function sin(πx/2)in the interval -1<=x<=1 using the first 4 Lefendre polynomials. Calculate both the L² and the max norms of the error (within a 5-10% accuracy is enough). Recall that P0=1, P1=x, P2=（3x²-1）/2, P3=（5x²-3x）/2 These are orthogonal, but not orthonormal