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Find the Area of a Right-angled Triangle Whose Hypotenuse is 13 Cm Long and One of Its Legs is 12 Cm Long. - Mathematics

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Question

Find the area of a right-angled triangle whose hypotenuse is 13 cm long and one of its legs is 12 cm long.

Sum

Solution

In right-angled Δ ABC,

Base BC = 12 cm

and hypotenuse AC = 13 cm

Applying Pythagoras Theorem,

(AC)2 = (AB)2 + (BC)2

(13)2 = (AB)2 + (12)2

169 = (AB)2 + 144

(AB)2 = 169 − 144

(AB)2 = 25

∴ AB =`sqrt25`

= `sqrt(5xx5)` = 5 cm

Now, area of Δ ABC =`1/2"base"xx"altitude"`

= `1/2xx12xx5` = 30 cm2

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Concept of Measurement Using a Basic Unit Area of a Square, Rectangle, Triangle, Parallelogram and Circle, Rings and Combined Figures.
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Chapter 20: Mensuration - Exercise 20 (B)

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Selina Concise Mathematics [English] Class 7 ICSE
Chapter 20 Mensuration
Exercise 20 (B) | Q 19
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