Skinny triangle

The skinny triangle is frequently used in astronomy to measure the distance to Solar System objects.

During the intervening period, the orbit of the Earth around the Sun moves the measuring station a great distance, so providing a very long baseline.

This baseline can be as long as the major axis of the Earth's orbit or, equivalently, two astronomical units (AU).

The distance to a star with a parallax angle of only one arcsecond measured on a baseline of one AU is a unit known as the parsec (pc) in astronomy and is equal to about 3.26 light years.

[6] The skinny triangle is useful in gunnery in that it allows a relationship to be calculated between the range and size of the target without the shooter needing to compute or look up any trigonometric functions.

Military and hunting telescopic sights often have a reticle calibrated in milliradians, in this context usually called just mils or mil-dots.

[7] Or, perhaps more usefully, a target 6 feet in height and measuring 4 MOA corresponds to a range of 1800 yards (just over a mile).

A simple form of aviation navigation, dead reckoning, relies on making estimates of wind speeds aloft over long distances to calculate a desired heading.

Since predicted or reported wind speeds are rarely accurate, corrections to the aircraft's heading need to be made at regular intervals.

Fig. 1 Isosceles skinny triangle
Fig.2 Length of arc l approaches length of chord b as angle θ decreases
Fig.3 The right skinny triangle