Strange values of approximating coefficients returned by matlab's wavelets decomposition

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I'm trying to get wavelet decomposition of arcsin(x) using, say, haar wavelets
When using both Matlab's dwt or wavedec functions, I get strange values for approximating coefficients. Since applying low-pass haar wavelets's filter equals to performing half-sum and the maximum of arcsin is pi/2, I assume that approximating coefficients can't surpass pi/2 yet this code:

x = linspace(0,1,128);
y = asin(x);
[cA, cD] = dwt(y, 'haar'); //cA for approximating coefficients

returns values more than pi/2 in cA. What am I doing wrong?