Question

Answer 1

\(A=\dfrac{1}{4}+3\cdot\dfrac{3}{4}=\dfrac{1}{4}+\dfrac{9}{4}=\dfrac{5}{2}\)

Answer 2

\(\Rightarrow\sin^2\alpha+\cos^2\alpha=\dfrac{1}{4}+\cos^2\alpha=1\\ \Rightarrow\cos^2\alpha=\dfrac{3}{4}\\ \Rightarrow\sin^2\alpha+3\cos^2\alpha=\dfrac{1}{4}+\dfrac{9}{4}=\dfrac{5}{2}\)