HP 49g+ - Manual (Page 48)

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Angle Measure
Trigonometric functions, for example, require arguments representing plane
angles. The calculator provides three different Angle Measure modes for
working with angles, namely:
• Degrees: There are 360 degrees (360
o ) in a complete circumference, or
90 degrees (90 o ) in a right angle. This representation is mainly used
when doing basic geometry, mechanical or structural engineering, and
surveying.
• Radians: There are 2π radians (2π r ) in a complete circumference, or π/2
radians ( π/2 r ) in a right angle. This notation is mainly used when solving
mathematics and physics problems. This is the default mode of the
calculator.
• Grades: There are 400 grades (400 g ) in a complete circumference, or
100 grades (100 g ) in a right angle. This notation is similar to the degree
mode, and was introduced in order to “simplify” the degree notation but
is seldom used now.
The angle measure affects the trig functions like SIN, COS, TAN and
associated functions.
To change the angle measure mode, use the following procedure:
• Press the H button. Next, use the down arrow key, ˜, twice. Select
the Angle Measure mode by either using the \key (second from left in
the fifth row from the keyboard bottom), or pressing the @CHOOS soft menu
key ( B). If using the latter approach, use up and down arrow
keys, — ˜, to select the preferred mode, and press the !!@@OK#@ F soft
menu key to complete the operation. For example, in the following
screen, the Radians mode is selected:
Coordinate System