cos²α+sin²α=1
cos²α=1-sin²α=1-(√2/2)²=1-2/4=1-1/2=1/2
cosα=√(1/2)=1/√2
tgα=sinα/cosα=(√2/2)÷(1/√2)=√2*√2/2=2/2=1
ctgα=cosα/sinα=(1/√2)÷(√2/2)=(1*2/(√2*√2))=2/2=1
