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Apply the Properties of Isosceles and Equilateral Triangles to Find the Unknown Angles in the Given Figure: - Mathematics

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Question

Apply the properties of isosceles and equilateral triangles to find the unknown angles in the given figure:

Sum

Solution

In fig.,

x = a + b

But b = y ..........(Angles opposite to equal sides)

Similarly a = c

But a + c + 30° = 180°

⇒ a + a + 30° = 180°

⇒ 2a + 30° = 180°

⇒ 2a = 180° − 30° = 150°

⇒ a =`(150°)/2=75°` and b + y = 90°

⇒ y + y = 90°

⇒ 2y = 90°

⇒ y =`(90°)/2=45°` ⇒ b = 45°

Hence x = a + b = 75° + 45° = 120° and y = 45°

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Concept for Angle Sum Property
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Chapter 15: Triangles - Exercise 15 (B)

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Selina Concise Mathematics [English] Class 7 ICSE
Chapter 15 Triangles
Exercise 15 (B) | Q 2.4
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