सिद्ध करो : ` (cos 70^(@))/(sin 20^(@))+ ( cos 59^(@))/( sin 31^(@))-8 sin^(2) 30^(@)=0`

Explanation

`LHS=( cos 70^(@))/( sin 20^(@))+( cos 59^(@))/( sin 31^(@))-8sin^(2) 30^(@)`
`implies LHS=( cos (90^(@)-20^(@)))/( sin 20^(@)) + ( cos (90^(@)-31^(@)))/( sin 31^(@))-8sin^(2) 30^(@)`
`implies LHS=( sin 20^(@))/( sin 20^(@))+ ( sin 31^(@))/( sin 31^(@))-8sin^(2) 30^(@) " " [:' cos (90^(@) - theta )= sin theta ]`
`implies =1+1-8((1)/(2))^(2)=2-2=0=RHS " "[ :' sin 30^(@)=(1)/(2)]`