Use a calculator to find the acute angle between the planes given below to the nearest hundredth of a radian.

nothingxplus$+33$yminus$33$zequals$=99,$

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$44$xplus$+$nothingyplus$+$nothingzequals$=77$

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Part $1$

The angle is

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radians.

$($Round to the nearest hundredth as$$ needed.$)$