`sin10^(@)sin50^(@)sin60^(@)sin70^(@)=(1)/(2)sin60^(@)sin10^(@)(2sin 70^(@)sin50^(@))`
`=(1)/(2)xx(sqrt3)/(2)sin10^(@)[cos(70^(@)-50^(@))-cos(70^(@)+50^(@))]`
`=(sqrt3)/(4)sin10^(@)(cos 20^(@)-cos 120^(@))`
`=(sqrt3)/(4)sin10^(@)(cos 20^(@)+(1)/(2))=(sqrt3)/(8)(2cos 20^(@)sin10^(@))+(sqrt3)/(8)sin10^(@)`
`=(sqrt3)/(8)[sin(20^(@)-10^(@))-sin(20^(@)-10^(@))]+(sqrt3)/(8)sin 10^(@)`
`=(sqrt3)/(8)sin 30^(@)=(sqrt3)/(8)xx(1)/(2)=(sqrt3)/(16)`
