CIRCLE DERIVATION OF AREA OF CIRCLE LETS TAKE d𝞡 , A VERY SMALL ANGLE IN ABOVE FIGURE SO; THE SMALL PART OF CIRCLE IN DIAGRAM CAN BE CONSIDERED AS RIGHT ANGLED TRIANGLE FROM ABOVE FIGURE, tan d𝞡= opposite side/ adjacent side tan d𝞡 = ds/r AS ANGLE IS VERY SMALL, tan d𝞡 = d𝞡 SO, d𝞡 =ds/r SO, ds=r d𝞡 ..................(1) AREA OF TRIANGLE= 1/2 * BASE *HEIGHT = 1/2 * r * ds D(A) = 1/2 * r *r d𝞡............. FROM (1) IF WE INTEGRATE THESE SMALL TRIANGLES HAVING THIS AREA, WE WILL GET AREA OF CIRCLE SO AREA OF CIRCLE= ∫D(A) 2𝜋 = ∫ 1/2* r