The upper two angles are A and B, with E in the middle and C and D below. Because ∠ACB and ∠CED are antipodal angles, the sum of the internal angles of the triangle is 180 degrees, so ∠ A+∠ B = ∠ C ∠ D.
Arrow:
The vertex is a, the base is b and c, and the included angle is d.
Connect AD and extend to point E. According to the external angle and nature of triangle, ∠BAD+∠ABD=∠BDE, ∠DAC+∠ACD=∠CDE.
Five-pointed star:
180 degrees
I don't have a diagram, but you can write the five angles as A, B, C, D, E, mark the angle of d E as ∠ 1, and mark the angle of BC as ∠2.
∠∠A+∠D+∠E =∠ 1
∴∠∠∠∠∠∠∠∠∠∠∠∠∠ 1 =∠∠∠∠∠∠∠∠∠∠∠∠∠8736
∵∠B+∠C+∠2= 180 degrees (the sum of the angles in the triangle is 180 degrees).
∴ ∠A+∠B+∠C+∠D+∠E= 180 degrees