हल कीजिए :
` sin theta + sin 2 theta + sin 3theta + sin 4 theta =0`

Explanation

`sin theta + sin 2theta + sin 3 theta + sin 4 theta =0`
` rArr (sin theta + sin 4 theta ) + (sin 2 theta + sin 3 theta) =0`
`rArr 2 sin .(5theta)/(2) cos. (3 theta)/(2) + 2 sin (5theta)/(2) cos .(theta)/(2)=0`
`rArr sin .(5 theta)/(2) cos .(3 theta)/(2) + sin .(5 theta)/(2) cos . (theta)/(2)=0`
`rArr sin. (5theta)/(2){ cos .(3 theta)/(2) + cos .(theta)/(2)}=0`
`rArr sin. (5theta)/(2){ 2 cos theta cos . (theta)/(2)}=0`
अब यदि `sin .(5 theta)/(2)=0 rArr sin.(5 theta)/(2)= sin npi rArr theta = (2npi)/(5)`
यदि `cos theta =0 rArr cos theta =cos (2n +1)(1)/(2)`
`:. , theta =(2n+1) .(pi)/(2)`