समीकरण ` cos theta+ cos 2 theta + cos 3 theta= 0` से ` theta` का व्यापक मान ज्ञात कीजिए ।

Explanation

` cos theta + cos 2 theta + cos 3 theta = 0 `
` rArr cos 3 theta +cos theta + cos 2theta = 0`
` rArr 2 cos 2 theta * cos theta + cos 2 theta = 0 `
`rArr cos 2 theta ( 2 cos theta + 1) = 0 `
` rArr cos 2 theta = 0 "या " 2 cos theta + 1 = 0 `
अब ` cos2 theta = 0 `
`rArr 2 theta = ( 2n+1) pi/4`
और `2 cos theta + 1 = 0 `
` rArr cos theta = -1/2`
` = -cos. pi/3 `
` = cos (pi - pi/3)`
` = cos. (2pi)/3 `
` rArr theta = 2npi pm (2pi)/3 `