Question

501
21. If tan A = 8/25, then cos 2A
400
400
1)
2)
561
561
3)
400
689
089​

Answer 1

Step-by-step explanation:

given

tan A=8/25

now we know that

cos 2A= (1 - tan^2 A)/(1 + tan^2 A)

= (1-64/625)/(1+64/625)

= (561/625)/(689/625)

=561/689

Answer 2

Answer:

The value of cos2A is equal to 561/689 when given the value of tanA is 8/25.

Step-by-step explanation:

We have given the value of tan A = 8/25

To find the value of cos 2A:

Write a formula of cos 2A in terms of tan A:

$cos2A=\frac{(1-tanA^{2})}{(1+tanA^{2})}$

Now, put the value of tan A in above formula:

⇒    $cos2A=\frac{1-(\frac{8}{25})^{2} }{1+(\frac{8}{25})^{2}}$

⇒    $cos2A=\frac{1-(\frac{64}{625}) }{1+(\frac{64}{625})}$

⇒    $cos2A=\frac{(\frac{625-64}{625}) }{(\frac{625+64}{625})}$

∴      $cos2A=\frac{561}{689}$

Therefore the value of cos 2A is equal to 561/689.