I found an answer from www2.jpl.nasa.gov

The Parallax Angle -- How Astronomers Use Angular Measurement ...

How do scientists measure this angle, and how does this information tell them the distance to the star? The Earth revolves around the Sun every year, so that every  ...

For more information, see The Parallax Angle -- How Astronomers Use Angular Measurement ...

I found an answer from www.khanacademy.com

Stellar distance using parallax (video) | Khan Academy

this technique only works because we have assumed that the earth's orbit is circular. ... Now, the distance from the earth to the sun varies from about .98 AU to 1.02 AU, ... true that the star we are trying to measure would have moved away from the earth after six months making it so that the triangle is not an isosceles triangle ...

For more information, see Stellar distance using parallax (video) | Khan Academy

I found an answer from en.wikipedia.org

Altair - Wikipedia

Altair designated α Aquilae is the brightest star in the constellation of Aquila and the twelfth brightest star in the night sky. It is currently in the G-cloud—a nearby ...

For more information, see Altair - Wikipedia

Step 1: Draw a figure based on the data provided.

Distance to the solar system from the star AC = 4.29 ly

Converting light years to parsec

The distance traveled by light in one year is one light year.

1 year of light = speed of light * 1 year [math] = 94608 * 10^{11} [math] m

4.29 ly = 4.29 * 94608 * 10^{11} = 405868.32*10^{11} m

4.29 ly = \frac{405868.32 *10^{11}}{3.08*10^{16}} = 1.32 \text{ persec }      \because 1 \text{ parsec } = 3.08 * 10^{16} m

Diameter of the earth AB=3*10^{11} m

Step 2: Calculating the parallax angle \theta

\theta = \frac{AB}{AC}

\theta = \frac{3* 10^{11}}{405868.32* 10^{11} }

\theta = 7.39 * 10^{-6}   

Hence, parallax angle \theta = 7.39 * 10^{-6} rad = 1.5 seconds