Solve the following equation
`(i) 5cos2theta+2cos^(2)"(theta)/(2)+1=0`, `-(pi)/(2) lt theta lt (pi)/(2)`
`(ii) sin7theta+sin4theta+sintheta=0`, `0 le theta le pi`
`(iii) tantheta+sectheta=sqrt(3)`, `0 le theta le 2pi`

Answer

`(i)(pi)/(3),(-pi)/(3)` `(ii) 0,(pi)/(4),(pi)/(2),(3pi)/(4),pi,(2pi)/(9),(4pi)/(9),(8pi)/(9)` `(iii) (pi)/(6)`