1 perpendicular to the center of the circle is a chord, that is, bisecting the chord and bisecting the central angle.

Therefore, the radius is 1/sin 1, and the arc length is the radius times the central angle.

That is, 2* 1/sin 1 is B.

2. Make an angle bisector with a central angle of 90 degrees and take a point on the bisector. When the distance from this point to the arc is equal to the distance from the radius, it is the center of the inscribed circle.

Let the radius of the inscribed circle be r.

Then r+ (radical number 2)*r= radius of great circle =L/(π/2)

Therefore, r=2(√2- 1)L/TT can be obtained.

Then S=π r (r should be square) = TT 4 (√ 2-1) 2/TT 2 =12-8 √ 2.l (square)/π.