हल कीजिए :
`sin theta + sin 7 theta = sin 4theta`

Explanation

`:. , sin theta + sin 7 theta =sin 4theta`
`sin 7theta + sin theta - sin 4 theta =0`
`2 sin 4 theta cos 3 theta - sin 4 theta =0`
` sin 4 theta [2 cos 3 theta -1] =0`
जब `sin 4 theta =0 ` तब
sin `4 theta = sin npi`
`4 theta =npi `
`theta =(npi)/(4)`
और जब ` 2 cos 3 theta -1=0` तब़
`2 cos 3 theta =1`
`cos 3 theta = (1)/(2) =cos .(pi)/(3)`
`cos 3 theta = cos (2 npi -+ (pi)/(3))`
` 3theta = 2npi -+(pi)/(3)`
` theta = (1)/(3) [2npi -+ (pi)/(3)]`
अतः `theta` के अभीष्ट मान `= (npi)/(4),(1)/(93)[2npi -+ (pi)/(3)]`