周期T=2(11π/12-7π/12)=2π/3
ω=2π/T=3,f(x)=Acos(3x+φ)
而f(¾π)=Acos(3×¾π+φ)=A,即cos(9π/4+φ)=1,
所以φ=﹣7π/4+2kπ,可取φ=¼π
f(½π)=Acos(3×½π+¼π)=﹣2/3,
可解得A=﹣(2√2)/3
所以f(x)=﹣(2√2)/3cos(3x+¼π)
————————不明白可以再问~
周期T=2(11π/12-7π/12)=2π/3
ω=2π/T=3,f(x)=Acos(3x+φ)
而f(¾π)=Acos(3×¾π+φ)=A,即cos(9π/4+φ)=1,
所以φ=﹣7π/4+2kπ,可取φ=¼π
f(½π)=Acos(3×½π+¼π)=﹣2/3,
可解得A=﹣(2√2)/3
所以f(x)=﹣(2√2)/3cos(3x+¼π)
————————不明白可以再问~