Answer:
The value of Cos 2a is - ( ) .
Step-by-step explanation:
Given as
Tan a =
Now, ∵ Tan Ф =
So, Tan a =
Or, =
Or, <u>From Pythagoras Theorem </u>
Hypotenuse² = perpendicular² + Base²
Or, Hypotenuse² = 12² + 5²
Or, Hypotenuse² = 144 + 25
Or, Hypotenuse² = 169
∴ Hypotenuse = = 13
Take Hypotenuse = 13
Now,∵ Cos 2Ф = Cos²Ф - Sin²Ф
So, Cos 2a = Cos²a - Sin²a
or , Cos 2a = 1 - 2 Sin²a ∵ Cos²a + Sin²a = 1
Or, Cos 2a = 1 - 2 ×( )²
Or , Cos 2a = 1 - 2 ×( )²
Or, Cos 2a = 1 - 2 × ()
Or, Cos 2a = ()
∴ Cos 2a = - ()
Hence the value of Cos 2a is - () . answer