ode>M</code>. For the expressions, see below. Real-valued spherical harmonics are also called tesseral harmonics, those with <code>L==M</code> are called sectorial harmonics, and those with <code>M=0</code> are called zonal harmonics.
</p>

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<div class="subtitle">Examples</div>

<p>
Plot the dependence on <code>theta</code> of the axial spherical harmonics with L = 7 and M = 0:
</p>

<pre class="matlab">
theta = linspace(0,pi);
phi = zero