Question 969246
{{{cos(4t)= (-sqrt(3))/2)}}}
From here,
{{{4t=(5/6)pi+2*pi*k}}} and {{{4t=(7/6)pi+2*pi*k}}}
Now divide both sides by 4.
{{{t=(5/24)pi+(pi/2)*k}}} and {{{t=(7/24)pi+(pi/2)*k}}}
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