a exact vs an exact

Some examples from the web:

• Or perhaps swimming might be more a exact description.
• Hydromechanics is a exact science, hydrostatics is an expanding science.
• Last week I did a exact replica to scale of Wrigley Field.
• A Exact-Tiegel... you ever use one of these?
• A chemical rocket exacts a huge weight penalty, because its entire fuel supply must be carried on board.
• No, bonnie, we need a more exact location than that.
• Astronomy is a very exact science.
• There must have been a more exact diagnosis.
• If you want a more exact location, you need to cut out the noise.
• If you call back on Tuesday, it looks like we may be able to give you a more exact time.
• If you're interested in a more exact science, spend time on geometry.
• In this way, we provide the possibility for producers to get a more exact idea of what they are buying.
• I must say, though, that we lack the statistical data to carry out a more exact and more precise analysis.
• Emphasis should be placed on the concept of relocation as a more exact description of the preparation process as the women approach their release date.
• However, we would have preferred to see a more exact definition of by-products and even higher recycling targets.
• It's all a question of exact timing and interface pressure.
• I might have to exact a price from whoever it is you're protecting.
• "Dispute over a woman" - exact words.
• I therefore also consider it essential to make a more exact distinction between data needed to fight crime and sensitive private data.
• More sophisticated auction procedures are more adapted where there is less certainty about market values and a more exact method of price discovery of each asset would be needed.

Some examples from the web:

• Spiritual matters have never been an exact science.
• Fingerprint analysis isn't an exact science.
• Why, it's an exact replica of your wedding dress.
• Say hello to an exact scale model of me.
• This is an exact replica of the helmet Amelia Earhart wore when she invented airplanes.
• They've been training in an exact replica of Division for months.
• This is an exact copy of the report commissioned by Cesare Borgia himself.
• It's an exact science, consistent as gravity.
• Geology's not an exact science.
• We need to build an exact replica of the Bellagio vault.
• Field work is not an exact science.
• We did not get content or an exact origin where the call came from.
• No, you give me an exact time.
• Various experts have been consulted, but an exact diagnosis has proved elusive.
• Except an exact timeline of your guilt.
• Everything in here is either real or an exact replica.
• It would be silly to name an exact dollar amount.
• It's an exact replica of my mom's.
• Capnomancy isn't an exact magic.
• I can make an exact copy of this guitar.