Find an equilateral triangle. There's a lot of hidden information there.
Did you catch red_dog's excellent hint?
Two quadrants within a square of length 10cm.
. . Find the area of the shaded region.
Label the square , starting at the upper-left and labelling clockwise.
Label the intersection of the two arcs with .
Draw radii and .
Triangle is equilateral with side 10cm.
. . I'm sure you can find its area.
Sectors and have radius 10 and central angles 30°.
. . and you can find their areas, too, right?
recall that the yellow regions are outlined by circular arcs with radius 10. consider the left arc. any line drawn from the bottom left corner to any point along the arc will have the length of the radius, which is 10. the same thing holds true for the arc on the right. since the base of the triangle drawn is one side of the square, it will have a length of 10 as well. thus we have a triangle with sides 10 units of length each, thus it is an equilateral triangle