Write the expression as the sine, cosine, or tangent of an angle. cos 8x cos 2x - sin 8x sin 2x

asked May 12, 2017 129k views

2 votes

Write the expression as the sine, cosine, or tangent of an angle.

cos 8x cos 2x - sin 8x sin 2x

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1 vote

cos 8x cos 2x - sin 8x sin 2x = 1/2 sqrt(2+sqrt(3)

Sultan Ali answered May 15, 2017

9.5k points

3 votes

cos(A - B) = cos(A)cos(B) - sin(A)sin(B)
Thus,
cos(8x)cos(2x) - sin(8x)sin(2x)
= cos(8x - 2x)
= cos(6x)

Huonderv answered May 19, 2017

8.1k points

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