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Master came in! Mathematics problems in senior high school entrance examination
My humble opinion should be 5/ 12. The top (60+90+60) is overlapped. It can be observed from the OA on one side of the sector and rotated 360 degrees. In fact, only the middle sector of 150 degrees is in quadrant I, so I personally think it should be 5/ 12.

When OA is in the first quadrant and the fourth quadrant, the condition is met. The effective angles are 90 degrees and 60 degrees respectively.