I believe it's<span> 8cos(x)⁸ - 16cos(x)⁶ + 10cos(x)⁴ - 2cos(x)².
</span>
<span>
Alternately, you can write [</span><span><span>1 / (tan(2x) - cot(2x))] + [cos(8x) / (tan(2x) - cot(2x))].
</span></span>
<span><span>
</span></span>
</span>
Alternately, you can write [</span><span><span>1 / (tan(2x) - cot(2x))] + [cos(8x) / (tan(2x) - cot(2x))].
</span></span>
</span></span>