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Henry is asked to find the exact value of [tex][tex]$\cos \frac{10 \pi}{3}$[/tex][/tex]. His steps are shown below.
1. Subtract [tex][tex]$2 \pi$[/tex][/tex] from [tex][tex]$\frac{10 \pi}{3}$[/tex][/tex] as many times as possible:
[tex][tex]$
\frac{10 \pi}{3}-2 \pi=\frac{4 \pi}{3}
$[/tex][/tex]
2. Find the reference angle for [tex][tex]$\frac{4 \pi}{3}: \frac{3 \pi}{2}-\frac{4 \pi}{3}=\frac{\pi}{6}$[/tex][/tex] :
3. The cosine value for [tex][tex]$\frac{\pi}{6}$[/tex][/tex] is [tex][tex]$\frac{\sqrt{3}}{2}$[/tex][/tex].
4. The cosine value is positive because [tex][tex]$\frac{\pi}{6}$[/tex][/tex] is in the first quadrant.

Which of the following describes Henry's errors?



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