Question

`"cos"  2 theta` is not equal to ____________.

विकल्प

• `2  "cos"^2 theta - 1`

• `1 - 2  "sin"^2 theta`

• `(1 + "tan"^2 theta)/(1 - "tan"^2 theta`

• `(1 - "tan"^2 theta)/(1 + "tan"^2 theta`

Answer 1

`"cos"  2 theta` is not equal to

`underline((1 + "tan"^2 theta)/(1 - "tan"^2 theta))`.

Explanation:

`"cos"  2 theta` is not equal to

`"cos" (theta + theta) = "cos" theta . "cos" theta - "sin" theta . "sin" theta = "cos"^2 theta - "sin" ^2 theta`

`= ("cos"^2 theta - "sin"^2 theta)/("cos"^2 theta + "sin"^2 theta)`

`= (1 - "tan"^2 theta)/(1 + "tan"^2 theta)`