Note that with respect to the above norm, $\cos(nx)$ is perpendicular to $\sin(nx)$ and perpendicular to $\cos(mx)$ for $n\ne m$.
+
+
+
+
+
+Note that with respect to the above norm, $\cos(nx)$ is perpendicular
+to $\sin(nx)$ and perpendicular to $\cos(mx)$ for
+$n\ne m$.
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+