This is an exercise in the third grade math book, which is to investigate the circle. The content of a circle has two right-angled triangles, one is the radius, and the distance from the radius to the chord is half of the chord, which constitutes a right-angled triangle, which is the basis for solving this problem. Let the radius be r, then the distance from the radius to the chord is R- 1, half of the chord length is 5, just r 2 = (r-1) 2+5 2, and solve the equation with R= 13.

The other right triangle is a triangle inscribed in a circle. If one side intersects the diameter, the angle opposite to the diameter is a right angle.

Remember these two right triangles? The first one is used to solve some calculation problems, and the second one often appears in proof questions ~

You can call me again in the future if you have any questions ~ ~