In a △ABC, ∠ABC = 30∘ and ∠ACB = 45∘. Which is the longest side in this triangle?
BC
Angles in △ABC are;
∠BAC = 180∘−(30∘+45∘)=105∘.
So, ∠BAC > ∠ACB > ∠CBA
As we know that the side opposite to the larger angle is longer than the side opposite to the smaller angle.
So, BC > AB > CA,
Therefore, the side opposite to the largest angle will be the longest side.
Hence, BC is the longest side.