Question

Areas related to circles class 10 exercise 12.3

Answer 1

radius of circle =r
area of circle=π*r*r
diameter =2r
circumference=2*π*r

Answer 2

in this exercise we need to use few formula

basics

area of circle = $\pi r^{2}$

circumference of circle = 2$\pi$r

area of sector = Theta/360 x $\pi r^{2}$

 area of segment = area of sector - area of triangle

if equilateral triangle = $\sqrt{3}$/4      x      $a^{2}$  

right angled tri. = 1/2 bh

unknown tri. with 2 sides and one angle = 1/2 a.b .  sin(theta)            

segment =  Theta/360 x $\pi r^{2}$ - 1/2 a.b .  sin(theta)