4sin10*sin50*sin70
=4sin10*cos40*cos20
=4sin10*cos10*cos20*cos40/cos10
=2sin20*cos20*cos40/cos10
=sin40*cos40/cos10
=sin80/2cos10
=cos10/2cos10
=1/2
4sin10*sin50*sin70
=4sin10*cos40*cos20
=4sin10*cos10*cos20*cos40/cos10
=2sin20*cos20*cos40/cos10
=sin40*cos40/cos10
=sin80/2cos10
=cos10/2cos10
=1/2