Respuesta :
The given trig function consist of trig values of common angles;
The values that represent the solution to [tex]\mathbf{cos \left(\dfrac{\pi}{4} - x\right)} = \dfrac{\sqrt{2} }{2} \cdot sin \, x[/tex], x ∈ [0, 2·π) are;
[tex]x = \left\{\dfrac{\pi}{2} , \, or \ \dfrac{3 \cdot \pi}{2} \right \}[/tex]
Reason:
The given function is presented as follows;
[tex]cos \left(\dfrac{\pi}{4} - x\right) = \dfrac{\sqrt{2} }{2} \cdot sin \, x[/tex]
Where;
x ∈ [0, 2·π)
We have;
cos(A - B) = cos(A)·cos(B) - sin(A)·sin(B)
[tex]cos \left(\dfrac{\pi}{4} \right) = \dfrac{\sqrt{2} }{2}, \ sin\left(\dfrac{\pi}{4} \right) = \dfrac{\sqrt{2} }{2}[/tex]
Which gives
[tex]cos \left(\dfrac{\pi}{4} - x\right) =\dfrac{\sqrt{2} }{2} \cdot cos \, x + \dfrac{\sqrt{2} }{2} \cdot sin \, x[/tex]
Therefore, we get;
[tex]\dfrac{\sqrt{2} }{2} \cdot cos \, x = \dfrac{\sqrt{2} }{2} \cdot sin \, x - \dfrac{\sqrt{2} }{2} \cdot sin \, x = 0[/tex]
cos x = 0
- [tex]cos \left(\dfrac{\pi}{2} \right) = 0[/tex]
Therefore;
- The possible solutions (x-values) to cos x = 0 are; [tex]0 \leq \dfrac{n \cdot \pi}{2} \leq 2 \cdot \pi[/tex]
Where;
n = 1, 3, 5, ...
x ∈ [0, 2·π)
We get;
- [tex]x = \left\{\dfrac{\pi}{2} , \, or \ \dfrac{3 \cdot \pi}{2} \right \}[/tex]
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