Concept:Use the tangent addition formula for A=60∘ and B=45∘.Explanation:Write 105∘ as 60∘+45∘.Apply the formula: tan(A+B)=1−tanAtanBtanA+tanBSo, tan105∘=tan(60∘+45∘)=1−tan60∘tan45∘tan60∘+tan45∘Substitute tan60∘=3 and tan45∘=1:tan105∘=1−3⋅13+1=1−33+1Since 3+1=1+3, this equals 1−31+3.Answer:Option C: 1−31+3