Review the proof of Cosine (StartFraction theta Over 2 EndFraction) = plus-or-minus StartRoot StartFraction 1 + cosine theta Over 2 EndFraction EndRoot.

A 2-column table with 8 rows. Column 1 is labeled Step with entries 1, 2, 3, 4, 5, 6, 7, 8. Column 2 is labeled Statement with entries cosine (2 x) = 2 cosine squared (x) minus 1, Let 2 x = theta, then x = StartFraction theta Over 2 EndFraction) minus 1, negative 1 + cosine (theta) = 2 cosine squared (StartFraction theta Over 2 EndFraction), StartFraction 1 + cosine (theta) Over 2 EndFraction = cosine squared (StartFraction theta Over 2 EndFraction), Cosine squared (StartFraction theta Over 2 EndFraction) = StartFraction 1 + cosine (theta) Over 2 EndFraction, cosine (StartFraction theta Over 2 EndFraction) = plus-or-minus StartRoot StartFraction 1 + cosine (theta) Over 2 EndFraction EndRoot.

Which step contains an error?

step 2
step 4
step 5
step 8