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问题: 三角函数

我求导变出一个很复杂的式子
可是不求导该怎么做
不会变啊....

解答:

显然a不等于0

(asinx+3)/(3cosx-4)>=-4
(asinx+3)/(4-3cosx)<=4
===> asinx+3 <=16- 12cosx
asinx+12cosx < = 13
根号(a^+12^)sin(x+b)<=13 ,tanb=12/a
a^+12^<= 13^
====>a^<=25 ...............(1)

(asinx+3)/(3cosx-4)< =4/7
===>7asinx -12cosx < = -37
根号(49a^+12^)sin(x-c)<= -37 ,tanc = 12/(7a)
49a^+12^ >= (-37)^
49a^> =1225
a^ >=25 ..................(2)

(1),(2) ====>a^=25 ===>a =5,或 -5