10.函数f(x)=3x−cosxf(x)=3x-\cos xf(x)=3x−cosx在(0(0(0,f(0))f(0))f(0))处的切线与直线2x−my+1=02x-my+1=02x−my+1=0垂直,则实数mmm的值为___−6-6−6___.