Solve the problem. (1) the circumference of a triangle is 68 cm, the length of side a is 30 cm, and the length of side B is 19 cm. How many cm is the length of side C? What triangle is this? (2) As shown in the figure, there is an isosceles triangle in an equilateral triangle, and ∠ 1 = 2, ∠ 3 = 4. Can you find the degree of ∠ 5?

Solve the problem. (1) the circumference of a triangle is 68 cm, the length of side a is 30 cm, and the length of side B is 19 cm. How many cm is the length of side C? What triangle is this? (2) As shown in the figure, there is an isosceles triangle in an equilateral triangle, and ∠ 1 = 2, ∠ 3 = 4. Can you find the degree of ∠ 5?

(1) The length of C is: 68-30-19 = 19 (CM), because there are two equal sides, so this triangle is isosceles triangle; answer: side length C is 19 cm, this is isosceles triangle. (2) because it is isosceles triangle, so the three internal angles are 60 degrees, and because ∠ 1 = 2, ∠ 3 = 4, so ∠ 1 = 3