() () 7 times () equals 29 () 3 find out what () should be

() () 7 times () equals 29 () 3 find out what () should be

327 times 9 = 2943
I hope you can adopt it
Please identify the first and fastest answer

The value of the algebraic expression 2cos10 °− sin20 ° cos20 ° is ()
A. 2B. 3C. 1D. 12

2cos10 °− sin20 ° cos20 ° = 2cos (300 − 20 °) − sin20 ° cos20 ° = 3cos200cos200 = 3, so select B

Vertical relationship
1. In the pyramid p-abcd, the bottom ABCD is a rectangle, the side PA is perpendicular to the bottom, and E and F are the midpoint of AB and CD respectively
(1) Verification: CD ⊥ PD
(2) If PA = PD, prove: PCD of EF ⊥ plane
2. In the square prism abcd-a1b1c1d1, Aa1 = 4, ab = 2, point E is on CC1 and C1E = 3ec, the proof is: A1C ⊥ plane bed
In question 1, PA = ad e, f are the midpoint of AB and PC respectively

1: 1): because CD ⊥ PA, CD ⊥ Da, DA / PA belong to planar pad, so CD ⊥ planar pad, because PD belongs to planar pad, so CD ⊥ PD2): because e and F are the midpoint of AB and PC respectively, triangle PAE and triangle EBC are congruent, so PE = EC, so triangle PEC is isosceles triangle. Because f is the midpoint of PC, so EF ⊥ PC