find missing angle?

**andyboy179** · January 17th 2011, 08:17 AM

hi, i need to find the missing angle from this shape:

im not really sure how to do this so if someone could tell me i will be very grateful!

**e^(i*pi)** · January 17th 2011, 08:27 AM

Have you covered the cosine rule?

$c^2=a^2+b^2-2ab\cos C$ which may also be written as $\cos C = \dfrac{a^2+b^2-c^2}{2ab}$

Edit: Misread angle as a side - use the law of sines instead (post left here for continuity)

**andyboy179** · January 17th 2011, 08:39 AM

would c^2= 6, a^2= 10 and b^2= 96??

**skeeter** · January 17th 2011, 08:50 AM

Law of sines ...

$\displaystyle \frac{\sin(96^\circ)}{10} = \frac{\sin{\theta}}{6}<br />$

solve for $\theta$

**e^(i*pi)** · January 17th 2011, 08:51 AM

Originally Posted by andyboy179

would c^2= 6, a^2= 10 and b^2= 96??

My apologies, I misread that angle as a side. Instead you can use the sine rule

$\dfrac{\sin A}{a} = \dfrac{\sin B}{b}$

In this case you have

$a = 6$
$\sin B = 96$
$b = 10$

$\sin A = \dfrac{a \sin B}{b} = \dfrac{6 \sin(96)}{10}$

**andyboy179** · January 17th 2011, 10:38 AM

would i start it like this?

**e^(i*pi)** · January 17th 2011, 10:43 AM

Yes, that's fine.

Me and skeeter used the other way of writing it which is the same as you but flipped over. I have started it off in post 6

**andyboy179** · January 17th 2011, 10:48 AM

would i then do sin?= 6x10/sin96=60.33?

Thread: find missing angle?

LinkBack

Thread Tools

Display

find missing angle?

Similar Math Help Forum Discussions

missing angle

missing angle

find missing angle?

work out missing angle?

missing angle

Search Tags