# Area of an oblique triangle question

• Feb 5th 2013, 02:37 PM
Danthemaths
Area of an oblique triangle question
Hello,
I need help with this question:
"There is a triangle OAB. The length of AO is 10m and AOB has an angle of 0.8c. This triangle also has an arc between points A and B."
Find the area of the triangle OAB
Find the area of the sector OAB

I have drawn the triangle to its correct description, see the attached image.

I have tried using the formula for the area of the sector 0.5r2θ, but I got the answer to be 2193. This might be right, just seemed too big. But I do not know the formula for the area of the triangle! (I suppose this triangle is different to the formula 0.5xbxh)

Dan
• Feb 5th 2013, 03:53 PM
Plato
Re: Area of an oblique triangle question
Quote:

Originally Posted by Danthemaths
Hello,
I need help with this question:
"There is a triangle OAB. The length of AO is 10m and AOB has an angle of 0.8c. This triangle also has an arc between points A and B."
Find the area of the triangle OAB
Find the area of the sector OAB

I have drawn the triangle to its correct description, see the attached image.

I cannot help you because I have no idea what $0.8^c$ could mean.
• Feb 5th 2013, 05:02 PM
Prove It
Re: Area of an oblique triangle question
Quote:

Originally Posted by Plato

I cannot help you because I have no idea what $0.8^c$ could mean.

It means 0.8 radians... C is the symbol for radians, it stands for "number of lengths of the radius on the Circumference".

I suppose we're assuming that it's a circular arc, which means OB = OA, correct?
• Feb 5th 2013, 11:44 PM
Danthemaths
Re: Area of an oblique triangle question
Yes OB=OA. And 0.8 radians = 57.3 degrees
• Feb 5th 2013, 11:47 PM
Prove It
Re: Area of an oblique triangle question
If the angle is measured in radians, the area of the triangle can be found using \displaystyle \begin{align*} A = \frac{1}{2}ab\sin{(C)} \end{align*} and the area of a sector can be found using \displaystyle \begin{align*} A = \frac{1}{2}r^2\theta \end{align*}.