# Thread: find trigo ratio

1. ## find trigo ratio

find trigo ratio

2. Since $\frac{\sqrt{3}+1}{2\sqrt{2}}=\frac{1}{2}\cdot\frac {\sqrt{2}}{2}+\frac{\sqrt{3}}{2}\cdot\frac{\sqrt{2 }}{2}$,

we can break it up and use ones we do know by using the addition formula

$sin(\frac{\pi}{6})=\frac{1}{2}$

$cos(\frac{\pi}{4})=\frac{\sqrt{2}}{2}$

$sin(\frac{\pi}{4})=\frac{\sqrt{2}}{2}$

$cos(\frac{\pi}{6})=\frac{\sqrt{3}}{2}$

Now, use the addition formula to put it together

It would appear that when we add them up we get

$\frac{\pi}{6}+\frac{\pi}{4}=\frac{5\pi}{12}$

So, $sin(\frac{5\pi}{12})$

See how to do that now?. Sometimes they're not so obvious so we have to do some gymnastics.

3. sorry i didn't learnt that additon formula

i don't understand how to get that
$
\frac{\pi}{6}+\frac{\pi}{4}=\frac{5\pi}{12}
$

$
\frac{\pi}{6}+\frac{\pi}{4}=\frac{5\pi}{12}
$

4. addition formula for sine: $sin(a+b)=sin(a)cos(b)+cos(a)sin(b)$

$sin(\frac{\pi}{6}+\frac{\pi}{4})=sin(\frac{\pi}{6} )cos(\frac{\pi}{4})+cos(\frac{\pi}{6})sin(\frac{\p i}{4})=sin(\frac{5\pi}{12})$
Put them together from the last post. and you get

$\frac{\sqrt{3}+1}{2\sqrt{2}}\approx{0.965925....}$

or 75 degrees $sin(75)=\frac{\sqrt{3}+1}{2\sqrt{2}}$