# Angles and Degrees!

• Jun 11th 2007, 09:10 PM
Sazza
Angles and Degrees!
I have to find the value of each pro-numeral, and show the steps of working.
I know it's an isosceles, and it's exactly like a traingle except it's on it's side, and it's pointing right.The bottom angles < > left and right are the pro-numerals b, and where the sides come up to meet the tip (top) the sides are equal, and the right side, near the tip, is 40*
How would i find the angle of the pronumerals??
• Jun 11th 2007, 09:39 PM
earboth
Quote:

Originally Posted by Sazza
I have to find the value of each pro-numeral, and show the steps of working.
I know it's an isosceles, and it's exactly like a traingle except it's on it's side, and it's pointing right.The bottom angles < > left and right are the pro-numerals b, and where the sides come up to meet the tip (top) the sides are equal, and the right side, near the tip, is 40*
How would i find the angle of the pronumerals??

Hello,

I've attached a sketch of the triangle.

You are expected to know that the sum of all interior angles of a triangle is 180°.

$\displaystyle s = 180^\circ = \alpha + \beta + \gamma$

You know that two angles are equal and the 3rd angle is 40°:

$\displaystyle \beta = \alpha \ \text{and } \gamma = 40^\circ$

Plug in the value into the equation given above:

$\displaystyle 180^\circ = \alpha + \alpha + 40^\circ$
$\displaystyle 180^\circ - 40^\circ = 2 \cdot \alpha$
$\displaystyle 140^\circ = 2 \cdot \alpha$
$\displaystyle 70^\circ = \alpha$