Question

If cos theta = x, then cos 2theta =​

Answer 1

Step-by-step explanation:

we know the formula cos 2# is 2cos2# - 1

so cos 2 theta is 2x^2 - 1

Answer 2

Answer:

±

2

1

cos 2θ=

2

−1

we know cos

2

θ=2cos

2

−1

2cos

2

θ=1−

2

1

=

2

1

.

cos

2

=

4

1

cos θ=

4

1

=

2

+1

∴ cos θ=±

2

1