Answer:
[tex] \displaystyle \angle4 = {108}^{ \circ} [/tex]
Step-by-step explanation:
the sum of the interior angles of a triangle is 180°
thus our equation is
[tex] \displaystyle {51}^{ \circ} + {51}^{ \circ} + \angle2 = {180}^{ \circ} [/tex]
simplify addition:
[tex] \displaystyle {102}^{ \circ} + \angle2 = {180}^{ \circ} [/tex]
cancel 102° from both sides:
[tex] \displaystyle \angle2 = {72}^{ \circ} \cdots \text{I}[/tex]
By straight line theorem we acquire:
[tex] \displaystyle \angle4 + \angle2 = {180}^{ \circ} [/tex]
substitute:
[tex] \displaystyle \angle4 + {72}^{ \circ} = {180}^{ \circ} [/tex]
cancel 72° from both sides:
[tex] \displaystyle \angle4 = {108}^{ \circ} [/tex]
hence, the measure of [tex]\angle 4[/tex] is 108°
