1.

If `acos2theta+bsin2theta=ch a salphaa n dbeta`as its roots , then prove that`tanalpha+t a nbeta=(2a b)/(a+c)``tanalpha+t a nbeta=(c-a)/(c+a)``tan(alpha+beta)=b/a`

Answer» Here, `acos2theta+bsin2theta = c`
`=>a((1-tan^2theta)/(1+tan^2theta)) +b((2tantheta)/(1+tan^2theta)) = c`
`=>a(1-tan^2theta)+2btantheta = c(1+tan^2theta)`
`=>(c+a)tan^2theta-2btantheta+(c-a) = 0->(1)`
Now, given equation has roots `alpha` and `beta`.
So, equation (1), will have roots `tan alpha` and `tan beta`.
`:.` Sum of the roots `= (-(-2b))/(c+a)`
`:. tanalpha+tanbeta = (2b)/(a+c)`


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