the perimeter of a right angle is 60 cm and its hypotenuse is 25 cm find the area of triangle
Answers
Perimeter of right angled triangle = length of 1st side + length of 2nd side + length of hypotenuse
60 cm = length of 1st side + length of 2nd side + 25 cm
60 cm - 25 cm = ;ength of 1st side + length of 2nd side
35 cm = length of 1st side + length of 2nd side
35 cm - length of 1st side = length of 2nd side ...( i )
Now,
By Pythagoras Theorem
⇒ ( length of 1st side )^2 + ( length of 2nd side )^2 = ( hypotenuse )^2
⇒ ( length of 1st side )^2 + ( 35 cm - length of 1st side )^2 = ( 25 cm )^2
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( a - b )^2 = a^2 + b^2 - 2ab
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⇒ ( length of 1st side )^2 + 1225 cm^2 + ( length of 1st side )^2 - 70( length of 1st side ) = 625 cm^2
⇒ 2( length of 1st side )^2 - 70( length of 1st side ) + 1225 cm^2 - 625 cm^2 = 0
⇒ 2( length of 1st side )^2 - 70( length of 1st side ) + 600 cm^2 = 0
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length of 1st side is written as x for convenience.
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⇒ 2x^2 - 70x + 600 = 0
⇒ x^2 - 35x + 300 = 0
⇒ x^2 - ( 15 + 20 )x + 300 = 0
⇒ x^2 - 15x - 20x + 300 = 0
⇒ x( x - 15 ) - 20( x - 15 ) = 0
⇒ ( x - 15 )( x - 20 ) = 0
⇒ x = 15 or x = 20
⇒ Length of 1st side = 15 or 20
If we subtract 15 from 35, we will get 20 . if we subtract 20 from 35 , we will get 15. So, we can say that the sides are 15 and 20.
Therefore, 1st and 2nd sides are 15 cm and 20 cm.As it is a right angled triangle.
Area = 1 / 2 × length of 1st side × length of 2nd side
Area = 1 / 2 × 15 cm × 20 cm
Area = 15 cm × 10 cm
Area of the right angled triangle is 150 cm^2.
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MARK AS BRAINLIEST