帮忙解个高中数学题！谢谢了

Question

已知命题p:x2-x-2大于等于零（m大于0）问（1）若p的否命题为真求x的取值范围（2）若q的否命题是p的否命题的充分不必要条件，求m的取值范围

Answer 1

1.由b^ =ac,根据正弦定理有:sinB^ =sinA*sinC,即: 1-cosB^ =-[cos(A C)-cos(A-C), 而由已知条件cos(A-C)=3/2-cosB,cos(A C)=cos(180-B)=-cosB 故1-cosB^ =cosB-(3/2-cosB)即:cosB^ 2cosB-5/2=0 则:(cosB 1)^ -7/2=0 cosB=√14/2-1 B=arccos(√14/2-1) 2.sinAcosC=3cosAsinC,即: sin(A C) sin(A-C)=3sin(A C)-3sin(A-C),即2sin(A C)=4sin(A-C), 亦即2sinB=4sin(A-C),sinB=sin(A-C)/2 而a*a-c*c=2b,根据正弦定理有sinA^-sinC^=2sinB即: (sinA sinC)(sinA-sinC)=2sinB,亦即:sin(A C)sin(A-C)=2sinB(和差化积的结果 即sinBsin(A-C)=2sinB,故sin(A-C)=2 因此:sinB=sin(A-C)/2=1 B=90