1) 42√6*cos п/6*cos 3п/4

[latex]42 \sqrt{6} *cos \frac{ \pi }{6} *cos \frac{3 \pi }{4} =42 \sqrt{6} * \frac{ \sqrt{3} }{2} *cos( \pi - \frac{ \pi }{4}) =[/latex][latex]=42 \sqrt{6} * \frac{ \sqrt{3} }{2} *(-cos \frac{ \pi }{4}) =-42 \sqrt{6} * \frac{ \sqrt{3} }{2} * \frac{ \sqrt{2} }{2} =-63[/latex]