Question

Giúp em với ạ

Answer 1

\(a,cos^2a+sin^2a=1\\ \Leftrightarrow\left(\dfrac{1}{3}\right)^2+sin^2a=1\\ \Leftrightarrow sin^2a=\dfrac{8}{9}\)

=> Câu a sai

b, \(sin^2b+cos^2b=1\\ \Leftrightarrow sin^2b+\left(\dfrac{1}{4}\right)^2=1\\ \Leftrightarrow sin^2b=\dfrac{15}{16}\\ \Rightarrow sin^2a+sin^2b=\dfrac{8}{9}+\dfrac{15}{16}=\dfrac{263}{144}>1\)

=> Câu b đúng