7) = 2*(√2/2)*(-1/2) - 1*(-√2/2) = -√2/2 + √2/2 = 0
8) = 1 +1/2 +2*3/4 = 1 + 1/2 +3/2 = 3
9) = 3 - 4*(-√3/2) * √3/2 = = 3 + 3 = 6
10) Sin5α Sin4α + Sin4αSin3α - Sin2αSinα =
=Sin4α(Sin5α + Sin3α) - Sin2αSinα = Sin4α*2Sin3αCosα - Sin2αSinα
(условие не дописано)