Cho một đường thẳng có điểm O,có goc xOy = 120°, yÔz = 30°,góc zOt = 60° và tOx = 30°.Chứng minh Om và On vuông góc với nhau,biết rằng : Om là tia phân giác của góc xOt và On là tia phân giác của góc yOz?

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