Answer:
The answer is a. cos2x - sin2x - sin x. Use the rule: cos2x = (cos^2)x - (sin^2)x. So, substitute cos2x in the expression: cos2x - sinx = ((cos^2)x - (sin^2)x) - sinx = (cos^2)x - (sin^2)x - sinx. Therefore, choice a. is correct choice.
Step-by-step explanation:
<u>Statements Reasons </u>
1 . ∠ABC and ∠CBD are a linear pair Given
2. m∠CBD = m∠EFG Given
3 . ∠ABC and ∠CBD are supplementary Definition of linear pair
4. m∠ABC + m∠CBD = 180° Definition of supplementary
5. m∠ABC + m∠EFG = 180° Substitution property
6. ∠ABC and ∠CBD are supplementary Definition of supplementary
This can be rewritten as
(x -6)² = 90 . . . . . the left side is already a perfect square
x -6 = ±√90 . . . . . take the square root
x = 6 ±3√10 . . . . add 6
