Use a double angle formula to rewrite the given expression. $$10 \cos ^ { 2 } x - 5$$
A) $5 \cos 5 x$
B) $5 \cos 2 x$
C) $10 \cos 2 x$
D) $2 \cos 10 x$
E) $2 \cos 5 x$

Question

Use a double angle formula to rewrite the given expression. $$10 \cos ^ { 2 } x - 5$$
A) $5 \cos 5 x$
B) $5 \cos 2 x$ ​
C) $10 \cos 2 x$ ​
D) $2 \cos 10 x$ ​
E) $2 \cos 5 x$ ​

Quizplus · Accepted Answer

The double angle formula for sine is: sin(2θ) = 2sin(θ)cos(θ)
We can rewrite 11ea99db_b444_8b98_94ac_e3fb77ccfdc2_TB4590_00 as sin(2θ), where θ = 19.5°
Then we have:
sin(2θ) = sin(2(19.5°)) = 2sin(19.5°)cos(19.5°)
This is equivalent to 11ea99db_b444_b2aa_94ac_0b1b0e3e684a_TB4590_11.

Use a Double Angle Formula to Rewrite the Given Expression 10cos⁡2x−510 \cos ^ { 2 } x - 510cos2x−5

Use a Double Angle Formula to Rewrite the Given Expression $10 \cos ^ { 2 } x - 5$