Question

请帮我解答几道数学题感激不尽 pre-calculate！！有过程的加悬赏！

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Answer 1

5 questions you should select c

The reasons are as follows:

∵secx=1/cosx=-√2
∴cosx=-√2/2
∵∏≤x≤3∏/2
∴x=-5∏/4

∴you should select c

6 questions you should select a

The reasons are as follows:

∵sin7∏/6=-1/2

sinx=-2/3

sin5∏/4=-√2/2

∴sin7∏/6>sinx>sin5∏/4

∴7∏/6<x<5∏/4

∵∏≈3.1415

∴3.665083<x<3.926875

∴ you should select a

7 questions you should select b

Correct for y=arctan(800/x) (x>0)

2 questions you should select b

3 questions you should select b

Answer 2

班有56个学生，其中男同学占全班人数的七分之三，转进几个男同学后，男2；解设：全部落的人数为x猎物为y 由题意得：｛y-x=4(1) {(x/6)*

Answer 3

I can't understand!!!!