已知正三棱锥ABC，点P，A，B，C都在半径为的求面上，若PA，PB，PC两

已知正三棱锥ABC，点P，A，B，C都在半径为的求面上，若PA，PB，PC两两互相垂直，则球心到截面ABC的距离为________。

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已知正三棱锥ABC，点P，A，B，C都在半径为的求面上，若PA，PB，PC两

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