Subtended angle definition - Math Open Reference (original) (raw)

| | | Subtended angle Definition: The angle formed by an object at a given external point Try thisDrag the orange dot representing the observer's eye, or the base of the flagpole. Note how the angle subtended by the flagpole to the observer's eye varies with distance. The Moon The moon subtends an angle of approximately 0.54° (32 arc-minutes) to an observer on the Earth. Of course, the moon's orbit is not constant or exactly circular, so this varies a little. But not by very much.If you hold up your thumb at arm's length, you can easily cover the full moon. This means your thumb subtends a larger angle to your eye at arm's length than the moon does at 380,000 kilometers. The Sun The sun, on the other hand, subtends an angle of approximately 0.52°(31 arc-minutes) to an observer on the Earth. This is a striking coincidence. By sheer chance, it is almost the same as the angle subtended by the moon. This is why, during a solar eclipse, that the moon almost exactly covers the sun.A Solar Eclipse Because they both subtend nearly the same angle to the earth, when the moon gets between the sun and the earth, it covers the sun almost exactly, causing a solar eclipse. During the eclipse a thin glittering ring can be seen around the disk. This is caused by hot glowing gases and other material streaming into space from the sun.The sun is about 150,000,000 kilometers from the earth, so clearly the sun must be vastly larger than the moon. Not to scale Other angle topics General Angle definition Degrees Radians Angle bisector Subtended angle Interior of an angle Included angle Angle Types Acute angle Right angle Obtuse angles Straight angle Reflex angle Full angle Angle relationships Vertical angles Complementary angles Supplementary angles Linear pair Adjacent angles Corresponding angles Alternate interior angles Alternate exterior angles Interior angles of a transversal Exterior angles of a transversal (C) 2011 Copyright Math Open Reference. All rights reserved | | | - | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | |