∴a+β=π/4 or π+π/4∵sina = √5/5 cos β=3√10/10 ∴cos a= 2√5/5 sinβ=√10/10 ∴sin(a+β)= sinacosβ+cosasinβ=√2/2已知锐角α,β∴a+β=π/4 or π+π/4
