Question

cos2theta= 1-tan2theta/1+ tan2theta is true or false prove it
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Answer 1

Answer:

false.

cos2theta=1-tan^2theta/1+tan^2theta.

proof_ take tan^2theta =sin^2theta/cos^2theta

if u substitute in it u will get cos^2theta-sin^2theta/cos^2theta+sin^2theta.

here,substitute sin^2theta=1-cos^2theta.

then u will get 2cos^2theta-1.

we know that cos^2theta is also =cos2theta.

so cos^2theta=1-tan^2theta/1+tan^2theta.

(Here, ^2means square.)

Answer 2

Answer:

false

Step-by-step explanation:

take theta as 30 degrees.

cos 2(30)= cos 60= 1/2

1- tan 2(30)= 1- tan 60 = 1-√3

1+tan 2(30)= 1+ tan 60=1+√3

1-√3/1-√3 do rationalising then u get -2 +√3

so both answers are not equal

it is false.