Question

cos(π +2a),если sin a=√0,3

Answer 1

cos(π+2a) = - cos2a = - (cos²a-sin²a) = - (1-2sin²a)= - (1 - 2 * 0.3) = - 0.4

Answer 2

$cos( pi +2 alpha )=-cos2a \ -cos2a=-(1-2sin^{2} a)= \ =-(1- (2*sqrt{0.3)}^{2} )=-(1-2*0.3) =-(1-0.6)= \ =-0.4$