Question

in an isosceles triangle the base angles are equal.the vertex angle is 40 degrees what are the base angles of the triangle?

Answer 1

Dear Student,


$$\begin{gathered} LettrianglebeABC \\ sumofallanglesofatriangleis180 \\ \Rightarrow \angle A+\angle B+\angle C=180 \\ let\angle Abevertexangleand\angle Band\angle Carebaseangleswhichareequal \\ hence\angle B=\angle C \\ \Rightarrow 40+\angle B+\angle C=180 \\ \Rightarrow \angle B+\angle C=180-40 \\ \Rightarrow \angle B+\angle C=140 \\ \Rightarrow 2\times \angle B=140 \\ \Rightarrow \angle B=70 \\ also\angle B=\angle C \\ hence\angle B=\angle C=70 \end{gathered}$$


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