Q7 of 39 Page 150

Let’s write the measurement of angles of triangle ABC if AB = BC and BAC + ACB = 50°

Given: ΔABC, BAC + ACB = 50° and AB = BC



To find the measurement of angles of the triangle ABC


Now in ΔABC, it is given AB = BC


We know angles opposite to equal sides are equal, therefore


⇒∠BAC = ACB……….(i)


Given BAC + ACB = 50°


Substituting values from equation (i) in the above equation, we get


⇒∠ACB + ACB = 50°


2ACB = 50°


⇒∠ACB = 25°…….(ii)


Substituting values from equation (ii) in equation (i), we get


⇒∠BAC = ACB = 25°……….(iii)


We also know in a triangle the sum of all three interior angles is equal to 180°.


So in this case,


BAC + ACB + ABC = 180°


Substituting the values from equation(iii) and given criteria, we get


ABC + 25° + 25° = 180°


ABC = 180° - 25° - 25°


ABC = 130°……(iv)


From equation (iii) and (iv), the required values of the angles are


BAC = ACB = 25°, ABC = 130°


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