If each internal angle of a triangle is greater than 60 degrees (at least one internal angle is less than or equal to 60 degrees), the sum of the three internal angles must be greater than 180 degrees, which contradicts the theorem that the sum of the internal angles of a triangle is 180 degrees, so the assumption is wrong and the original conclusion is correct.

It is known that EC=30m ∠BED=90 degrees ∠BDE=30 degrees, ∴BE= 10√3≈ 17.3 (using the tangent of a triangle) ∴ BC = be = BED = 65438+.

Pass the question on, I don't have a book.