Which expression is equivalent to cos(1.4x) − cos(0.6x)?

a. -2sin x sin(0.4x)

b. 2sin x sin(0.4x)

c. -2cos x cos(0.4x)

d. 2cos x cos(0.4x)

  A.  -2sin(x)sin(0.4x)

Step-by-step explanation:

At x=0, the given expression evaluates to zero.

For x near zero, the given expression is slightly negative. You know this because cos(1.4x) decreases faster than cos(0.6x), so their difference will be negative.

Of the answer choices, you can eliminate C and D because they are not zero at x=0. You can eliminate choice B, because it is positive for values of x near zero. The only viable choice is A:

   -2sin(x)sin(0.4x)

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Of course, a graphing calculator can help you figure this out. See the attachment. The given expression is plotted using a solid red line; the answer choice A is plotted using blue dots.

a line is an defined derm because it

a)contains an infinite number of points b) can be used to create other geometric shapes c)describes something that does not have width or depth d) is a term that does not have a formal definition. a line is an undefined term because it: contains an infinite number of points.

answer: i believe the answer is e

step-by-step explanation: