What is the value of COS square 5 π / 12 + cos square π / 12 + cos5 π / 12cos π / 12

cos(5π/12)^2+cos（π/12）^2+cos(5π/12)cos(π/12)
=sin(π/12)^2+cos（π/12）^2+sin(π/12)cos(π/12)
=1+sin(π/6)/2
=5/4

3.9.11.17.20 () () 39.41 what is the law

Odd items:
3+8=11
11+9=20
therefore
20+10=（30）
30+11=41
Even items:
9+8=17
17+10=（27）
27+12=39
So: 3.9.11.17.20 (27) (30) 39.41