# Parallax equation

please can somebody help me with this parallax equation:

D=distance to star
theta=angle
using the rule D=(d/2)/tan(theta/2)
when d = 300*10tothe6
and theta = 5*10tothe-5

what is the distance to the star in km and light years?

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#### Doc Al

Mentor
What's the problem?

(d is in what units?)

d is in km and theta is in degrees.
This is as close as i can get:
for this answer i get a result of:

343774677078406.6587981892079753

So, is this answer the number of km?

what is this answer in exponential form? ie: 34 * 10tothepower13?

1 light year is 9.467*10tothepower12, so in light years i think the distance will be:
27 light years

Please let me know if i am right

#### Doc Al

Mentor
D and d have the same units. Your value for D in km is correct, but you messed up the conversion to light years. Do it over, more carefully.

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