Sin 17° × cos 43°= √2 × sin Alfa - 1=

sin17*cos43° =1/2*(sin(17° - 43°) +sin(17°+ 43°) = 1/2*(sin(17°- 43°) +sin60°) =1/2*(√3/2 - sin26°)  =√3*/4 -sin26°/2 . *********************************************************************************************** √2*sinα -1 =√2*(sinα - 1/√2) =√2*(sinα - sin30°) =2√2sin(α-30°)/2*sin(α+30°)/2.