'fundamental in determining' is correct and usable in written English.
You can use it when you are talking about something that plays an essential role in a decision or process. For example, "Accurate data collection is fundamental in determining the success of research."
Despite being fundamental in determining its physical state, a star's age cannot be measured directly, and estimation methods are imprecise.
The joint effect of various ocean variables on extreme responses of offshore structures is fundamental in determining the design loads.
Therefore, the proxy efficiency is fundamental in determining the total cost and productivity (number of simultaneous clients served by the system) to the VoD service.
The identification of pigment elements of the pottery of a site is fundamental in determining the site's cultural and temporal context.
However, the correctness and accuracy of position information in the node's list of neighbors is crucial and fundamental in determining the performance of position-based routing protocols [3].
Conducting accurate intellectual assessments in children who are deaf and hard-of-hearing is fundamental in determining and designing interventions and educational services.
Having signalled in a speech in December 1996 that he feared 'irrational exuberance' had taken over from the economic fundamentals in determining the prices of dotcom stocks, he stood back and watched as the S& P 500 index more than doubled, from 650 when he issued his warning, to its peak above 1,500.
The fundamental consideration in determining forgery is "intent to deceive".
This year, Citizens Union, whose endorsements are widely sought by politicians throughout the state, made promoting change in Albany a fundamental factor in determining which candidates it would support.
Detection of vibrations on the lunar surface by seismographs is of fundamental importance in determining the internal structure, physical state, and tectonic (crustal) activity of the Moon.
Road friction plays a fundamental role in determining the skidding risk.
