WEBVTT

00:00:00.000 --> 00:00:02.840
This is College Physics Answers
with Shaun Dychko.

00:00:03.390 --> 00:00:06.360
We are going to measure this parallax angle
between the Earth

00:00:06.500 --> 00:00:10.520
and this distant star which is 4 light years
directly above the Sun

00:00:11.130 --> 00:00:13.710
and we can draw this triangle here

00:00:13.710 --> 00:00:15.980
where this leg is 4 light years;

00:00:15.980 --> 00:00:18.730
this leg is the Earth-Sun distance

00:00:18.940 --> 00:00:21.850
and this <i>Θ 2</i> is the angle
we want to find.

00:00:22.520 --> 00:00:26.270
Now the tangent of <i>Θ 2</i> is going to be
the opposite, which is 4 light years,

00:00:26.270 --> 00:00:29.680
divided by the adjacent which is
the Earth-Sun distance

00:00:29.680 --> 00:00:33.920
and we can find the angle by taking
the inverse tangent of both sides.

00:00:34.610 --> 00:00:38.280
So the angle is the inverse tangent of four
light years converted into kilometers

00:00:38.480 --> 00:00:41.380
divided by the Earth-Sun distance
in kilometers

00:00:41.380 --> 00:00:44.210
giving essentially 90 degrees to two
significant figures

00:00:44.210 --> 00:00:47.060
or 89.99977 degrees.