If the equation is cos x*sqrt 3 = 3*sqrt (3*sin x), we'll
raise to square both sides to remove the square root from both
sides:
3(cos x)^2 = 9*3*sin
x
We'll divide by 3 both
sides:
(cos x)^2 = 9*sin
x
We'll use the Pythagorean identity to express cos x with
respect to sin x:
(cos x)^2 = 1 - (sin
x)^2
1 - (sin x)^2 = 9*sin
x
We'll subtract 9sin x both
sides:
- (sin x)^2 - 9*sin x + 1 =
0
(sin x)^2 + 9*sin x - 1 =
0
We'll replace sin x by
t:
t^2 + 9t - 1 = 0
We'll
apply quadratic formula:
t1 = [-9 + sqrt(9^2 -
4*1*(-1))]/2*1
t1 =
(-9+sqrt85)/2
t1 = 0.1097
t2 =
(-9-sqrt85)/2
t2 = -9.1097
sin
x = t1 => sin x = 0.1097 => x = arcsin 0.1097 => x = 6.2980 degrees
(1 st quadrant) or x = 180 - 6.2980 = 173.702 degrees (2 nd
quadrant)
sin x = -9.1097 impossible since the values of
the function sine cannot be smaller than
-1.
Therefore, the solutions of the equation
are expressed in degrees and they are: {6.2980 ;
173.702}.
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