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

User Onlyjus
by
2.9k points

1 Answer

4 votes

Answer:

cosA = -
(7)/(25)

Explanation:

Using the double angle identity

cos2A = 2cos²A - 1 , then

cosA = 2cos²(
(A)/(2) ) - 1 , that is

cosA = 2 × (
(3)/(5) )² - 1

= 2 ×
(9)/(25) - 1

=
(18)/(25) -
(25)/(25)

= -
(7)/(25)

User Stepan Kasyanenko
by
3.2k points
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