Answer:
<em>Explanation below</em>
Step-by-step explanation:
<u>Angles in a Triangle</u>
There are two basic relations of angles we need to recall:
- Supplementary angles add up to 180°
- Internal angles of a triangle add up to 180°
Note a, b, and c are the internal angles of the triangle. The angle c is what is needed to a+b to complete 180°, thus:
c = 180 - ( a + b )
Also, note c and d are supplementary angles. Again, c is what is needed to d to complete 180°, thus
c = 180 - d
From the two relations above, it follows that:
a + b = d
