1)sinα=2/√5, cos²α=1-sin²α, cos²α=1-4/5=1/5, cosα=-1/√5т.к.α∈(π/2;π). tgα=sinα/cosα tgα=(2/√5)÷(-1/√5)=-2 2)√3-√12·sin²5π/12=√3-2√3(1-cos5π/6)/2=√3-√3+√3·(-1/2)=-√3/2 3)18(sin²24-cos²24)÷cos48=18(sin²24-cos²24)÷(cos²24-sin²24)=-18 4)2^(3,4)·5^(2,4)/10^1,4=10^(2,4)·2/10^(1,4)=10·2=20