Question 1177441
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{{{4cos(6*theta)=0}}}
{{{cos(6*theta)=0}}}<br>
On the interval 0 to 2pi, cosine theta is 0 twice -- at pi/2 and 3pi/2.  Cosine of 6*theta will be 0 6*2=12 times on that interval; the first two zeros will be at (pi/2)/6 and (3pi/2)/6, or pi/12 and 3pi/12.  Of course you might want to simplify that second zero to pi/4, but that's not absolutely necessary.<br>
The separation between successive zeros of cosine theta is pi; the separation between zeros of cosine of 6*theta is pi/6 or 2pi/12.<br>
The zeros of {{{4cos(6*theta)}}} on the interval 0 to 2pi:<br>
pi/12, 3pi/12, 5pi/12,..., 19pi/12, 21pi/12, 23pi/12<br>