The fundamental frequency (first harmonic) of a vibrating string corresponds to a standing wave pattern where the length of the string is equal to half of the wavelength (\(\lambda\)) of the wave. 

Given that the guitar string is 75 cm long, the wavelength of its fundamental note can be calculated using the formula:
\(\lambda = 2L\)

where:\(\lambda\) = wavelength\(L\) = length of the string

Substitute the values:\(\lambda = 2 \times 75\)\( \lambda = 150 \, cm \)

Therefore, the wavelength of the fundamental note of the guitar string is 150 cm.