首页 > 留学知识库

问题: 过程啊~~~

设f(x)=asin(πx+α)+bcos(πx+β)+4(a,b,α,β为常数),且f(2008)=5,那么f(2009)=?

解答:

设f(x)=asin(πx+α)+bcos(πx+β)+4(a,b,α,β为常数),且f(2008)=5,那么f(2009)=?
解:f(2008)=5→asin(2008π+α)+bcos(2008π+β)+4=5
asin(α)+bcos(β)+4=5→asin(α)+bcos(β)=1.....(**)
∴f(2009)=asin(2009π+α)+bcos(2009π+β)+4
=asin(π+α)+bcos(π+β)+4
=-asin(α)-bcos(β)+4
=-[asin(α)+bcos(β)]+4(由(**))
=-1+4
=3