## anonymous one year ago Will MEDAL Cos(sin2/3 + tan3/2) Sum and Difference Formula Can someone do this problem and tell me what they get so I can compare it with my own

1. UsukiDoll

so.. we're dealing with $\cos(\theta+ \beta)$ where $\theta = \sin \frac{2}{3}, \beta = \tan \frac{3}{2}$ ?

2. UsukiDoll

$\cos( \theta+ \beta) = \cos(\theta)\cos(\beta)-\sin(\theta)\sin(\beta)$

3. UsukiDoll

|dw:1433138555024:dw|

4. UsukiDoll

if my beta is tangent then I have to find cosine and sine of my beta|dw:1433138769787:dw|

5. UsukiDoll

$\sin(\beta) = \frac{3}{\sqrt{13}}, \cos(\beta) = \frac{2}{\sqrt{13}}$

6. UsukiDoll

$\cos( \theta+ \beta) = \cos(\theta)\cos(\beta)-\sin(\theta)\sin(\beta)$ $\sin(\beta) = \frac{3}{\sqrt{13}}, \cos(\beta) = \frac{2}{\sqrt{13}}$ $\sin(\theta) = \frac{2}{3}, \cos (\theta) = \frac{\sqrt{5}}{3}$

7. UsukiDoll

$\cos( \theta+ \beta) =((\frac{2}{\sqrt{13}})-\frac{2}{3}(\frac{3}{\sqrt{13}})$ code broke |dw:1433139398171:dw|

8. anonymous

That's what I got, thanks so much

9. UsukiDoll

=) whew.. that was a nerve wrecking one due to the way it was written so I had to reread a part of my notes and see what was going on ^^