Before starting to enter the angle measure to calculate the value of a trigonometric
function (sine, cosine, tangent) you must make sure that the current angle unit (degree, radian, grad) the calculator
is configured to be using is the same that your problem requires. For instance, if you are solving a problem in which the angles are given in degrees you must verify that the calculator is configured to work in degrees.
When calculator is turned on, the angle unit is reset to degrees, but just to make sure it still is, look at the display: It should show the indicator DEG. If the display indicator is not DEG press the key [DRG] once or twice until you see the DEG on the screen.
The angle unit being taken care of, we turn to the actual calculation
Usually, to calculate the sine of an angle, you enter the angle value, press the [SIN] key and hit [=]. As you can see the sine function eats the number stored in its current register and calculates its sine.
To make sure that the calculator is taking the sine of 65 and not of 25*65, I would enter the calculation as follows [65 [SIN] [*] 25 [=
] : the result should be 22.65769468
] 65 [SIN] [ )
In the last key sequence, the use of parentheses forces the calculator to pause all previous calculations and wait for the closing right parenthesis. When the right parenthesis is entered, the calculator takes care of the contents of the parentheses first, then resumes the operations entered before the parentheses.Importance of checking the angle unit before a calculation
Let us perform the calculation with angle unit
- in degrees : 25* sin(65) = 22.65769468
- in radians : 25 *sin(65) = 20.67071699
As you can see, the two values are not very far apart and since you are expecting a value that does not exceed 25 you might want to check your result.
Hope it helps.
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