Sum and Difference of Cosine

Which of the following is the same as  $\cos\ \left(A+B\right)$  

•  $\sin A\cos\ B\ +\ \cos\ A\ \sin\ B$  

•  $\sin\ A\ \cos\ B\ -\ \cos\ A\ \sin\ B$  

•  $\cos\ A\ \cos\ B\ +\ \sin\ A\ \sin\ B$  

•  $\cos\ A\ \cos\ B\ -\ \sin\ A\ \sin\ B$  

Tags

CCSS.HSG.SRT.C.7

Expand  $\cos\ \left(\frac{\pi}{5}+\frac{\pi}{6}\right)$  

•  $\cos\frac{\pi}{5}\cos\frac{\pi}{6}-\sin\frac{\pi}{5}\sin\frac{\pi}{6}\$  

•  $\cos\frac{\pi}{5}\cos\frac{\pi}{6}+\sin\frac{\pi}{5}\sin\frac{\pi}{6}\$  

•  $\cos\ \frac{2\pi}{11}$  

•  $\cos\frac{\pi}{5}\sin\frac{\pi}{6}-\cos\frac{\pi}{5}\sin\frac{\pi}{6}\$  

Tags

CCSS.HSG.SRT.C.8

 $\cos75^o\cos15^o-\sin75^{o\ }\sin15^o$  is equivalent to

•  $\sin\ 90^{o\ }$  

•  $\sin\ 60^{o\ }$  

•  $\cos\ 90^{o\ }$  

•  $\cos\ 60^{o\ }$  

Tags

CCSS.HSF.TF.C.9

Use sum or difference angles identity to find the exact value for  $\cos105^o$  

•  $\frac{\sqrt{6}+\sqrt{2}}{4}$  

•  $\frac{\sqrt{6}-\sqrt{2}}{4}$  

•  $\frac{-\sqrt{6}-\sqrt{2}}{4}$  

•  $\frac{\sqrt{2}-\sqrt{6}}{4}$  

Tags

CCSS.HSF.TF.C.9

Find the exact value of the expression.
cos(20)cos(40) - sin(20)sin(40)

• 1/4
• 1/2
• √(3)/2
• √(3)

Tags

CCSS.HSF.TF.C.9

Please choose the correct sum and difference formula:
cos (α-β) =

• sin α cos β + cos α sin β
• sin α cos β - cos α sin β
• cos α cos β - sin α sin β
• cos α cos β + sin α sin β

Tags

CCSS.HSF.TF.C.9

If  $\sin A=\frac{3}{5},\sin B=\frac{2}{3},$   $and\ \angle A\ and\ \angle B$  are acute angles, what is the value of  $\cos\left(A-B\right)?$  

•  $-\frac{2}{3}$  

•  $\frac{4\sqrt{5}-6}{15}$  

•  $\frac{4\sqrt{5}+2}{5}$  

•  $\frac{4\sqrt{5}+6}{15}$  

Tags

CCSS.HSF.TF.C.9