Answer:
cos(a)
Step-by-step explanation:
I substituted it on a calculator:
a = 30
b = 45
1/2 [ cos (a + b) + cos (a - b)]
1/2 [ cos (30 + 45) + cos (30 - 45)] = Sqrt6/4
cos(a)cos(b)
cos(30)cos(45) = Sqrt6/4
C. cos(a) × cos (b) = 1/2 [cos (a+b) + cos (a-b)]
a = 30
b = 45
1/2 [ cos (a + b) + cos (a - b)]
1/2 [ cos (30 + 45) + cos (30 - 45)] = √6/4
cos(a)cos(b)
cos(30)cos(45) = √6/4.
Since -x is the same angle as x reflected across the x-axis, sin(-x) =-sin(x) as sin(-x) reverses it's positive and negative halves sequentially when you think of the coordinates of points on the circumference of the circle in the form p = (cos(x),sin(x)).
Cos2x is one of the double angle trigonometric identities as the angle in consideration is a multiple of 2, that is, the double of x. Let us write the cos2x identity in different forms: cos2x = cos2x - sin2x. cos2x = 2cos2x - 1. cos2x = 1 - 2sin2x.
To learn more about trigonometric angle, refer
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