The altitude of a right triangle is 7 cm less than its base. If the hypotenuse is 13 cm, find the other two sides.
Answers
Let us say, the base of the right triangle be x cm.
Given, the altitude of right triangle = (x – 7) cm
From Pythagoras theorem, we know,
Base^2 + Altitude^2 = Hypotenuse^2
∴ x^2 + (x – 7)^2 = 132
⇒ x^2 + x^2 + 49 – 14x = 169
⇒ 2x^2 – 14x – 120 = 0
⇒ x^2 – 7x – 60 = 0
⇒ x^2 – 12x + 5x – 60 = 0
⇒ x(x – 12) + 5(x – 12) = 0
⇒ (x – 12)(x + 5) = 0
Thus, either x – 12 = 0 or x + 5 = 0,
⇒ x = 12 or x = – 5
Since sides cannot be negative, x can only be 12.
Therefore, the base of the given triangle is 12 cm
and
the altitude of this triangle will be (12 – 7) cm = 5 cm.
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↓↓YOUR ANSWER↓↓
Given, hypotenuse = 13 cm
Let the base be x cm.
Then altitude = (x - 7) cm
Using Pythagoras theorem
♦ (Hypotenuse)² = (Base)² + (Altitude)²
So,
♦ (13)² = ( x )² + ( x - 7 )²
♦ 169 = x² + x² + 49 - 14x
♦ 169 - 49 = 2x² - 14x
♦ 120 = 2 ( x² - 7x )
♦ 120/2 = x² - 7x
♦ 60 = x² - 7x ......(1)
From eq (1)
♦ x² - 7x = 60
♦ x² - 7x - 60 = 0
♦ x² - (12 - 5)x - 60 = 0
♦ x² - 12x + 5x - 60 = 0
♦ x(x - 12) + 5(x - 12) = 0
♦ (x + 5) ( x - 12) = 0
Hence,Value of x
1) x + 5 = 0
x = -5
which is not possible because x is length.
2) x - 12 = 0
x = 12
So,the value of x is 12 cm.
Hence, Altitude = 12 - 7 = 5 cm
And x is base itself = 12 cm
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