Straight LineMedium
Question
The graph of the function cos x cos (x + 2) - cos2 (x + 1) is
Options
A.a straight line passing through (0, - sin2 1) with slope 2
B.a straight line passing through (0, 0)
C.a parabola with vertex (1,-sin2 1)
D.a straight line passing through the point 
and parallel to the x-axis
and parallel to the x-axisSolution
Let y = cos x cos (x + 2) - cos2 (x - 1)
= cos (x + 1 - 1) cos(x + 1 - 1) - cos2 (x + 1)
= cos2 (x + 1) - sin2 1- cos2 (x + 1)
y = -sin2 1
This is a straight line which is parallel ro x-axis.
It passes throught (π / 2,- sin21)
= cos (x + 1 - 1) cos(x + 1 - 1) - cos2 (x + 1)
= cos2 (x + 1) - sin2 1- cos2 (x + 1)
y = -sin2 1
This is a straight line which is parallel ro x-axis.
It passes throught (π / 2,- sin21)
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