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(1) According to the encircling method in Figure 2, the length of AB is equal to the perimeter of the bottom of triangular prism, and ∴AB=30.

∫ Paper bandwidth is 15, ∴ SIN ∠ DAB = SIN ∠ ABM =, ∴ DAB = 30.

(2) in fig. 3, the triangular prism is truncated along the side passing through point a, and a side development diagram as shown in fig. a is obtained.

Translate △ABE in Figure A by 30cm to the left and △CDF by 30cm to the right to form a parallelogram ABCD as shown in Figure B,

This parallelogram is the parallelogram ABCD in Figure 2.

From the meaning of the question, we know that BC=BE+CE=2CE=2×,

The required length of rectangular paper tape is MB+BC=30? cos30 + = cm。