Question

Write the expression as the sine, cosine, or tangent of an angle. Sin 9x cos x-cos 9x sinx

Answer 1

Hint:  $\bf sin({{ \alpha}} + {{ \beta}})=sin({{ \alpha}})cos({{ \beta}}) + cos({{ \alpha}})sin({{ \beta}}) \\ \quad \\ sin({{ \alpha}} - {{ \beta}})=sin({{ \alpha}})cos({{ \beta}})- cos({{ \alpha}})sin({{ \beta}})\\\\ -----------------------------\\\\ thus\qquad sin(9x)cos(x)-cos(9x)sin(x)=\boxed{?}$