Respuesta :
cos (3π/4) can be written as,
cos (π-π/4) = -cosπ/4 = -1/√2
similarly sin3π/4=sin(π-π/4) = sin π/4 = 1/√2
cos (π-π/4) = -cosπ/4 = -1/√2
similarly sin3π/4=sin(π-π/4) = sin π/4 = 1/√2