Question

упростите выражение: 1)sin^2 t-1 2) (1-cos t)(1+cos t) 3)sin^2 t+2cos^2 t-1 

Answer 1

$sin^2 t-1=-cos^2t \ (1-cos t)(1+cos t) =1-cos^2t=sin^2t \ sin^2 t+2cos^2 t-1 =1-1+cos^2 t=cos^2 t$