Question

тригонометрия !!!!!!!!
последний пример

Answer 1

$(1-cos2x)ctgx=sinx \ ctgx= frac{cosx}{sinx} \ cos2x=cos^{2}x-sin^{2}x \ (1-( cos^{2}x-sin^{2}x) frac{cosx}{sinx} =sinx \ (1- cos^{2}x+sin^{2}x) {cosx} =sin^{2}x \ cos^{2}x+sin^{2}x=1 \ (1-1)cosx=sin^{2}x \ sin^{2}x =0 \ x= pi + pi k$