sin(x+pi/6) + cos(pi/3) -x) =
1
First we will use trigonometric identities to
solve.
We know that:
sin(a+b)
= sina*cosb + cosa*sinb
==> sin(x+pi/6)=
sinx*cos(pi/6) + cosx*sin(pi/6)
==> sin(x+pi/6)=
(sqrt3 /2 )*sinx + (1/2)*cosx......(1)
cos(a-b)= cosa*cosb
+ sina*sinb
==> cos(pi/3 -x)= cospi/3*cosx +
sinpi/3*sinx
==> cos(pi/3 -x) = (1/2) cosx + sqrt3
/2 * sinx............(2)
Now we will add (1) and
(2):
==> 2(sqr3/2)sinx + 2(1/2)cosx =
1
==> sqr3*sinx + cosx =
1
==> sqrt3 sinx = 1-
cosx
Square both
sides:
==> 3sin^2 x = 1 - 2cosx + cos^2
x
==> 3(1-cos^2 x) = 1- 2cosx + cos^2
x
==> 3 - 3cos^2 x = 1- 2cosx + cos^2
x
==> 4cos^2 x - 2cosx -2 =
0
==> 2cos^2 x - cosx -1 =
0
==> (cosx -1) (2cosx +1) =
0
==> cosx = 1 ==> x = 0, pi,
2pi
==> 2cosx +1 = 0 ==> cosx = -1/2
==> x = 4pi/3 , 5pi/3
==> x = {
0, pi, 4pi/3, 5pi/3, 2pi }
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