The perimeter of a right-angled triangle is 24 cm, and the area is 24 cm ^ 2. Find all the sides of the triangle.
It is known that the perimeter of a right-angled triangle is P = 24 cm, and the area is S = 24 cm2.
It is necessary to determine the lengths of the sides of a right-angled triangle, where the legs are A, B, and the hypotenuse is C.
We write down the formula for finding the perimeter and area, and also express C through A and B.
1) P = A + B + C.
Whence we get that A + B = 24 – C.
2) S = ½ * A * B.
Whence we get that AB = 24: ½ = 48.
3) C ^ 2 = A ^ 2 + B ^ 2.
We transform the third equality by adding 2 * A * B to both sides of it.
C ^ 2 + 2AB = A ^ 2 + B ^ 2 + 2AB.
C ^ 2 + 2AB = (A + B) 2.
Substitute the values from expressions 1 and 2.
C ^ 2 + 2 * 48 = (24 – C) 2.
Let’s open the brackets and solve the equation.
C ^ 2 + 96 = 576 – 48C + C2.
48C = 576 – 96.
48C = 480.
C = 10.
It turns out that the length of the hypotenuse is 10 cm.
Now we will find the sides by solving the system of equations.
3) A ^ 2 + B ^ 2 = 10 ^ 2.
4) AB = 48.
Multiply the 4th equation by -2 and add to the 3rd.
A2 – 2AB + B ^ 2 = 10 ^ 2 – 48 * 2.
(A – B) ^ 2 = 22.
A – B = 2.
Recall that A + B = 10.
Let’s add the last 2 equations.
2A = 12.
A = 6.
Now we define B.
B = 10 – A.
B = 10 – 6.
B = 4.
Answer: the lengths of the sides of a right-angled triangle are 4, 6, 10.