SChand Composite Mathematics Class 7 Chapter 11 Triangle and it's Properties Exercise 11C

 Exercise 11 C 

Question 1 

Find the lettered angle in each of the following : 

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Question 2

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Sol: $\angle M=20^{\circ}$

$\angle L+\angle M+\angle N=180^{\circ}$

$b=180^{\circ}-(20+20)$

$b=180^{\circ}-40=140^{\circ}$

Angle opposite equal sides of an isosceles triangle are equal 

Question 3  

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Sol: $m=50^{\circ}$

$\begin{aligned} x &=180^{\circ}-100 \\ x &=30^{\circ} \end{aligned}$

Question 4

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Sol: $\angle Q=59^{\circ}$

$x=180-\left(59^{\circ}+59^{\circ}\right)$

$x=180-118^{\circ}$

$x=62^{\circ}$ Ans

$x=32^{\circ}+y \quad=y=30^{\circ}$

$62-32^{\circ}=y$

Question 5

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Sol:

 $\begin{aligned} \angle D &=63^{\circ} \\ \angle D A E &=180^{\circ}-\left(63^{\circ}+63^{\circ}\right) \\ &=180^{\circ}-126^{\circ} \\ &=180^{\circ}-126^{\circ}=54^{\circ} \\ \angle B+\angle C+54^{\circ}=180^{\circ} \\ x+x &+54^{\circ}=180^{\circ} \end{aligned}$

$2 x=180^{\circ}-54^{\circ}$

$x=\frac{126}{2}$ $x=63^{\circ}$