# Math Help - Angles of triangle

1. ## Angles of triangle

in attachments

2. you should be very familiar with the first equation ...

$m\angle{1} + m\angle{2} + m\angle{3} = 180^{\circ}$

since $m\angle{3} + m\angle{4} = 180^{\circ}$ ( a linear pair)

$m\angle{1} + m\angle{2} + m\angle{3} = m\angle{3} + m\angle{4}$

so ...

$m\angle{1} + m\angle{2} = m\angle{4}$