Question

sinα×cosα(tgα-ctg(-α))

Answer 1

$sina*cosa(tga-(-ctga))=sina*cosa*(tga+ctga)=\\=sina*cosa*( frac{sina}{cosa} + frac{cosa}{sina})=sina*cosa* frac{sin^2a+cos^2a}{sina*cosa}=\\=sina*cosa* frac{1}{sina*cosa}=1$