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If `tanalpha=1/7,sinbeta=1/(sqrt(10)),`prove that`alpha+2beta=pi/4`, where `0

Answer» `sin beta = 1/sqrt10`
`:. cos beta = sqrt(1-(1/sqrt10)^2) = 3/sqrt10`
`:. tanbeta = sinbeta/cosbeta = 1/3`
Now, `tan2beta = (2tanbeta)/(1-tan^2beta) = (2/3)/(1-1/9) = 6/8 = 3/4`
Now, `tan(alpha+2beta) = (tanalpha+tan2beta)/(1-tanalphatan2beta)`
`=(1/7+3/4)/(1-1/7(3/4)) = (25/28)/(25/28) = 1`
`:. tan(alpha+2beta) = tan (pi/4)`
`:. alpha+2beta = pi/4.`


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