Page 66 and application1:(1) 20,26 (2) 36 (3) 64216 (4) 39,1022: (1)/kloc-0. 4. The number of pellets in the fifth pile is 1+2+3+4+5= 15. The number of pellets in the eighth pile is 1+2+3+4+5+6+7+8=36 69 pages 1. Difference: A straight line has no endpoint, a ray has only one endpoint, and a line segment has two endpoints. When two straight lines intersect at an angle of 90 degrees in the same plane, they are perpendicular to each other. On the same plane, two straight lines are always parallel to each other. 3. The second picture is large; 35 degrees bigger. 4. The circular angles of acute angle, right angle and obtuse angle are omitted. Page 69 Finishing and application: 1, omitting 2, angle 1= angle 2 = 120 angle 3= angle 4 = 40 angle 5 = 30 angle 6 = 60 angle 5+ angle 6 = 90 angle 3, omitting 4, (65438+) ...