Will mark brainliest drag and drop an answer to each box to correctly complete the derivation of a formula for the area of a sector of a circle.

Let
A-----> area of a sector of the circle
∅ -----> central angle is in radians
r------> the radius of the circle

 we know that

the ratio of a sector area A to the circle area is equal to the ratio of the central angle to the measure of a full rotation of the circle. A full rotation of the circle is 2*pi radians
so
A/(pi*r²)------> ∅/(2*pi)
multiply by (pi*r²)
A=[∅/(2*pi)]*(pi*r²)-------> A=(∅/2)*r²

therefore
the answer in the attached figure

No a triangle cannot be formed because when you add the two smallest number together (which would be 11) the have to be bigger than the number it is "against" ( which would be 12)