mitchelsewbaran
Write the expression as either the sine, cosine, or tangent of a single angle.



This Question is Closed


sirm3d
Best Response
You've already chosen the best response.
1
the problem resembles that of a cosine of a difference of two angles

sirm3d
Best Response
You've already chosen the best response.
1
\[\cos (AB)=\cos A \cos B + \sin A \sin B\]

mitchelsewbaran
Best Response
You've already chosen the best response.
0
so is it cosin(pi/5 pi/7)?

mitchelsewbaran
Best Response
You've already chosen the best response.
0
@sirm3d?

sirm3d
Best Response
You've already chosen the best response.
1
that's right.

sirm3d
Best Response
You've already chosen the best response.
1
you should combine pi/5pi/7 into one angle, as required in the problem.

mitchelsewbaran
Best Response
You've already chosen the best response.
0
cos π/7?

sirm3d
Best Response
You've already chosen the best response.
1
\[\frac{\pi}{5}\frac{\pi}{7}=\frac{7\pi5\pi}{35}=\frac{2\pi}{35}\]