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प्रश्न
If A = 300 , verify that:
(ii) cos 2A = `(1- tan^2A)/(1+tan^2A)`
उत्तर
A = 300
⇒ 2A = 2 × 300 = 600
(ii) cos 2A = cos `60^0 = 1/2`
`(1- tan62 A)/(1+ tan^2 A) = (1-tan^2 30^0)/(1+ tan^2 30^0)= (1-(1/sqrt(3))^2)/(1+(1/sqrt(3))^2` = `(1-(1/3))/(1+(1/3)) = ((2/3))/(4/3) = (2/3)xx3/4=1/2`
∴ cos 2A = `(1-tan^2A)/(1+ tan^2A)`
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