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2 years ago

If cosх A/2 =3/5, find the value of cos A

Mathematics

1 answer:

nikitadnepr [17]2 years ago

5 0

Answer:

cosA = - $\frac{7}{25}$

Step-by-step explanation:

Using the double angle identity

cos2A = 2cos²A - 1 , then

cosA = 2cos²( $\frac{A}{2}$ ) - 1 , that is

cosA = 2 × ( $\frac{3}{5}$ )² - 1

= 2 × $\frac{9}{25}$ - 1

= $\frac{18}{25}$ - $\frac{25}{25}$

= - $\frac{7}{25}$

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If cosх A/2 =3/5, find the value of cos A​

If cosх A/2 =3/5, find the value of cos A