  Ncert solutions

# Question 1

Q1) Find the value of the unknown exterior angle x in the following diagrams:      Solution 1:

(i) \angle A\ +\ \angle B+\ \angle C\ =\ 180\degree { angle sum property of triangle }

70\degree+\ 50\degree+\ \angle B\ =\ 180\degree

\angle B\ =\ 180\degree-\ 120\degree

\angle B\ =\ 60\degree

(ii) \angle BAC\ +\angle ACB\ =\ x\ {an exterior angle of a triangle is equal to the sum of the opposite interior angle }

65\degree+45\degree=x

110\degree=x

(iii) \angle CAB+\angle ABC\ =\ x {an exterior angle of a triangle is equal to the sum of the opposite interior angle }

30\degree+40\degree\ =\ x\

70\degree=x

(iv) \angle BCA+\angle CBA\ =\ x {an exterior angle of a triangle is equal to the sum of the opposite interior angle }

60\degree+60\degree\ =\ x

120\degree=x

(v) \angle A+\angle B=\ x {an exterior angle of a triangle is equal to the sum of the opposite interior angle }

50\degree+50\degree=\ x

100\degree=\ x\

(vi) \angle A+\angle B\ =\ x\ {an exterior angle of a triangle is equal to the sum of the opposite interior angle }

30\degree+60\degree\ =\ x\

90\degree=\ x

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