Question

if cos A =1/3 then find the value of cos 2A

Answer 1

Step-by-step explanation:

4

$4 \sqrt[2]$

Answer 2

$Given \: Cos \: A = \frac{1}{3} \: --(1)$

$Value \: of \: cos \: 2A$

$= 2 cos^{2} A - 1$

$= 2 \times \Big( \frac{1}{3}\Big)^{2} - 1$

$= 2 \times \frac{1}{9} - 1$

$= \frac{2}{9} - 1$

$= \frac{ 2 - 9 }{9}$

$= \frac{-7}{9}$

Therefore.,

$\red{ Value \: of \: cos \: 2A }\green { = \frac{-7}{9}}$

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