Answer:
See Below.
Step-by-step explanation:
We want to verify the trigonometric identity:
[tex]\cos^2(5x)-\sin^2(5x)=\cos(10x)[/tex]
For simplicity, we can let u = 5x. Therefore, by substitution, we acquire:
[tex]\cos^2(u)-\sin^2(u)[/tex]
Recall the double-angle identity formula(s) for cosine:
[tex]\displaystyle \begin{aligned} \cos(2x)&=\cos^2(x)-\sin^2(x)\\&=2\cos^2(x)-1\\&=1-2\sin^2(x)\end{aligned}[/tex]
Therefore, our identity becomes:
[tex]=\cos(2u)[/tex]
Back-substitute:
[tex]=\cos(2(5x))=\cos(10x)\stackrel{\checkmark}{=}\cos(10x)[/tex]
Hence proven.
