Step-by-step explanation: ◾As we have given the two sides of triangle, let the three sides of triangle are (a) , (b), (c) . ◾And perimeter of given triangle is 10.5 cm ◾were, let us assume the sides are, side a = 4.5 cm side b = 10 cm side c = ? we know, ◾perimeter of triangle = sum of all sides of triangle 10.5 = side a + side b + side c 10.5 = 4.5 + 10 + side c 10.5 = 14.5 + side c 10.5 - 14.5 = side c side c = 4 cm [side be never in negative ] therefor, ◾Now, we can use Hero's formula to find the area of triangle when sides of triangle are given. ◾Hero's formula Hero's formula for area of triangle = √[ s ( s - a ) ( s - b) (s - c) ] ◾For using this formula, we need to find the s (semiperimeter) S = [side a + side b + side c ] / 2 = [ 4.5 + 10 + 4 ] / 2 = 9.25 cm Therefor , ◾Area of triangle abc = √[ s ( s - a ) ( s - b) (s - c) ] = √[ 9.25 ( 9.25 - 4.5 ) ( 9.25 - 10 ) (9.25 - 4 ) ] = √ [ 9.25 (( 4.75 ) ( -0.75 ) ( 5.25 ))] =√ [( (9.25 ) (-3.5625) ( 5.25 )) = √[ ((48.5625) ( (-3.5625)) ] = √ [ 173 ( approximately) ] = 13.15 ( approximately) ◾In the above, (-3.5625)) we taken as a (3.5625 ) because area is never as an imaginary . ◾here, we took a value (13.15) as an approx, up-to two decimals . ◾So, the area of a triangle whose sides are 4.5 cm and 10 cm and perimeter 10.5 [Area ]=