At each corner of a triangular field of sides 26 m. 28 m and 30 m, a cow is tethered by a rope of, length 7 m. The area (in m ) ungrazed by the cows is

Area of the triangular field = $$\sqrt{s(s-a)(s-b)(s-c)}$$ , where , s = $$\frac{a+b+c}{2}$$
Area = $$\sqrt{42(42-26)(42-28)(42-30)}$$
= 336
Here radius of sectors, r = 7 m and let the angle at the corners be x,y,z.
area that can be gazed = $$\frac{x}{360}\pi r^{2}+\frac{y}{360}\pi r^{2}+\frac{}{360}\pi r^{2}$$
= $$\frac{x}{360}\pi r^{2}+\frac{y}{360}\pi r^{2}+\frac{}{360}\pi r^{2}$$
= $$\frac{x+y+z}{360}\pi r^{2}$$
= $$\frac{180}{360}\frac{22}{7}7^{2}$$
Thus the area of the plot that can be grazed is 77 sq m.
the area that can't be grazed = 336 - 77 = 259