The phrase "approximately known" is correct and usable in written English.
It means something is known or understood to a degree of accuracy that is not exact, but close enough to be considered reliable or sufficient. Example: "The exact location of the lost city may never be discovered, but its approximate location is believed to be somewhere in this region."
In this research, it is assumed that the amount of delay is approximately known, as is the approximated model of the plant.
Both types of star have a special property: Their intrinsic brightness is approximately known, so their distance from Earth can be estimated from their apparent brightness on the sky.
A third method entails the use of mean parallaxes of a star of a given proper motion and apparent magnitude; this yields a statistical sample of stars of approximately known and uniform distance.
Lundmark used novae that had been observed in the Andromeda Nebula to establish the distance of that nebula by assuming that these novae would have the same average absolute brightness as novae in the Milky Way whose distances were approximately known.
The best that can be done is to estimate the degree of difference between the languages in question, taking into account all that is known about them, and then compare this estimate with the estimated degrees of difference within families of languages such as the Romance family whose actual time of divergence is approximately known.
The response function is an only approximately known function of a specified linear function.
High-quality cRNA was hybridised to the HG-U95Av2 oligonucleotide microarray, which contains 12 599 gene probe sets, representing approximately 9670 known genes, plus approximately 1495 EST clones (Affymetrix, Santa Clara, CA, USA).
Purified DNA was amplified, labeled and hybridized to Affymetrix Promoter Tiling arrays with probes spanning 10 kb regions around the promoters of approximately 25,000 known human genes.
United States officials say that approximately 2,700 known or suspected Qaeda operatives have been detained or arrested around the world since Sept. 11.
Many copies of the book have been found in Egyptian tombs, but none contains all of the approximately 200 known chapters.
There are approximately 4,400 known naturally occurring minerals on Earth today (Hazen et al. 2008).
