Question

What are the amplitude and period of the function:
f(x) = 4 + 8cos(7x)cos(10) - 11sin(9x)sin(8)?

Answer 1

4+8cos7xcos10x-11sin9xsin8x

Answer 2

4+4cos17x+4cos3x+5.5cos17x-5.5cosx=4+9.5cos17x+4cox3x-5.5cosx
T=[2pi/17,2pi/3,2pi]=2pi/51[3,17,51]=2pi*51/51=2pi
you cannot determine the amplitude so it is more than 4+9.5+4-5.5=12
and less than 4+9.5+4+5.5=23

Answer 3

if you want to get exact amplitude you must take derivation so it is going to get hard!!

Answer 4

Cool, thanks so much for your help.