HP 35s Manual page 4

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HP 35s Solving Trigonometry Problems
In RPN mode, the calculation can be done like this:
5º=3º=Ù7º=Ã2¯5¯3¯ºl
In algebraic mode, calculate:
ºl4º=5ÕÙº=3Õú=7ÕÕ¯2¯5¯3Ï
Answer: The angle opposite the 7 inch side is 120 degrees. This means that three tiles will fit together exactly with
this angle pointing inwards, as they would make up 360 degrees.
Example 5: A ladder is leaning against a vertical wall. The ladder is 6 meters long and the foot of the ladder is 3 meters
from the base of the wall. What is the angle between the top of the ladder and the wall?
Solution: In RPN mode, divide the side opposite the angle by the long side and get the arc sine:
3Ï6¯ºi
In algebraic mode, press:
ºi3¯6Ï.
Answer: The ladder is at an angle of 30 degrees from the wall.
Example 6: A vector has components –5 in the X direction and –8 in the Y direction. In what direction does it point?
Solution: It would be possible to divide –5 by –8 and calculate the arc tangent, giving approximately 32 degrees, but
this would not specify the quadrant in which the vector lies. Fortunately, the 35s complex display modes
provide a way to view the complete arc tangent function that recognizes in which quadrant an angle lies.
The solution is the same in either RPN or algebraic mode.
First, set the display mode to rΘa.
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Figure 6
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Figure 8
- 4 - HP 35s Solving Trigonometry Problems - Version 1.0