b Let's measure

∠ 1

of Triangle I using a protractor.

We can see that the measure of $∠ 1$ is $14 0^{\circ} .$ With this, we will find the angle measures of the other angles.

$m ∠ 1$	$m ∠ 5$	$m ∠ 4$	$m ∠ 3$
$14 0^{\circ}$	$m ∠ 5 = 18 0^{\circ} - m ∠ 1 m ∠ 5 = 4 0^{\circ}$	$m ∠ 4 = m ∠ 5 m ∠ 4 = 4 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - (m ∠ 4 + m ∠ 5) m ∠ 3 = 10 0^{\circ}$

Next, we will measure $∠ 2 .$

We can see that the measure of $∠ 2$ is $8 0^{\circ} .$ Let's use the measures of the other angles using $m ∠ 2 .$

$m ∠ 2$	$m ∠ 3$	$m ∠ 4$	$m ∠ 5$
$8 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - m ∠ 2 m ∠ 3 = 10 0^{\circ}$	$m ∠ 4 = \frac{m ∠ 2}{2} m ∠ 4 = 4 0^{\circ}$	$m ∠ 5 = m ∠ 4 m ∠ 5 = 4 0^{\circ}$

Using the same way, we can calculate the angles measure of the other triangles. Let's start with using $∠ 1 .$

	$m ∠ 1$	$m ∠ 5$	$m ∠ 4$	$m ∠ 3$
Triangle I	$14 0^{\circ}$	$m ∠ 5 = 18 0^{\circ} - m ∠ 1 m ∠ 5 = 4 0^{\circ}$	$m ∠ 4 = m ∠ 5 m ∠ 4 = 4 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - (m ∠ 4 + m ∠ 5) m ∠ 3 = 10 0^{\circ}$
Triangle II	$13 0^{\circ}$	$m ∠ 5 = 18 0^{\circ} - m ∠ 1 m ∠ 5 = 5 0^{\circ}$	$m ∠ 4 = m ∠ 5 m ∠ 4 = 5 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - (m ∠ 4 + m ∠ 5) m ∠ 3 = 8 0^{\circ}$
Triangle III	$12 0^{\circ}$	$m ∠ 5 = 18 0^{\circ} - m ∠ 1 m ∠ 5 = 6 0^{\circ}$	$m ∠ 4 = m ∠ 5 m ∠ 4 = 6 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - (m ∠ 4 + m ∠ 5) m ∠ 3 = 6 0^{\circ}$

Now we will do the same thing for $∠ 2 .$

	$m ∠ 2$	$m ∠ 3$	$m ∠ 4$	$m ∠ 5$
Triangle I	$8 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - m ∠ 2 m ∠ 3 = 10 0^{\circ}$	$m ∠ 4 = \frac{m ∠ 2}{2} m ∠ 4 = 4 0^{\circ}$	$m ∠ 5 = m ∠ 4 m ∠ 5 = 4 0^{\circ}$
Triangle II	$10 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - m ∠ 2 m ∠ 3 = 8 0^{\circ}$	$m ∠ 4 = \frac{m ∠ 2}{2} m ∠ 4 = 5 0^{\circ}$	$m ∠ 5 = m ∠ 4 m ∠ 5 = 5 0^{\circ}$
Triangle III	$12 0^{\circ}$	$m ∠ 3 = 18 0^{\circ} - m ∠ 2 m ∠ 3 = 6 0^{\circ}$	$m ∠ 4 = \frac{m ∠ 2}{2} m ∠ 4 = 6 0^{\circ}$	$m ∠ 5 = m ∠ 4 m ∠ 5 = 6 0^{\circ}$

Exercise