Question

In ∆ABC, ∠A = 40° and ∠B = 60°. Then the longest side of ∆ABC is
(a) BC
(b) AC
(c) AB
(d) cannot be determined

Answer 1

(c) AB

In triangle ABC, we have:
$\angle A=40°,\angle B=60°$ ...(Given)
$$\begin{gathered} \mathrm{Here},\angle A+\angle B+\angle C=180° \\ \Rightarrow 60°+40°+\angle C=180° \\ \Rightarrow \angle C=80° \end{gathered}$$
∴ The side opposite to$\angle C$, i.e., AB, is the longest side of triangle ABC.