In the square grid, ∠ AOB is placed as shown in the figure, then sin ∠ AOB = () A. 55B. 255C. 12D. 2

As shown in the figure, if EF ⊥ ob is made, then EF = 2, of = 1. According to Pythagorean theorem, OE = 5, ≁ sin ∠ AOB = efoe = 25 = 255

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