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Trigonometry

Convert between degrees and radians

Change an angle from degrees to radians and back with the calculator.

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Half a turn is 180 degrees or π radians. To change degrees into radians multiply by π ÷ 180. To change radians into degrees multiply by 180 ÷ π.

Several models have a ready-made key or menu entry so you do not have to type that fraction.

Classic Graphing 84

Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.

  1. In radian mode, the degree symbol converts for you. Type 90, then open the ANGLE menu (2nd apps) and pick 1 for the degree sign.

    902ndANGLEapps1

  2. Press enter. 90 degrees is 1.570796327 radians (π ÷ 2).

    enter

You should see1.570796327

Classic Graphing 84 key reference

Natural Scientific 991

Start on the main screen: Press MENU, then 1 (Calculate) to return to the main calculation screen. AC clears the line you are on.

  1. In degree mode, type 1, open the angle-unit menu with OPTN then 2, and pick 2 for the radian sign.

    1OPTN22

  2. Press =. One radian is 57.29577951 degrees.

    =

You should see57.29577951

Natural Scientific 991 key reference

Natural Color Graphing

Start on the main screen: Press MENU then 1 to open Run-Matrix, the main calculation screen. Press EXIT to back out of a bar or screen, and SHIFT then EXIT (QUIT) to return to the app start.

  1. Type the plain formula 90 × π ÷ 180. π is SHIFT then the ×10ˣ key.

    90×SHIFTπ×10ˣ÷180

  2. Press EXE. The exact answer is π/2.

    EXE

You should seeπ/2

Natural Color Graphing key reference

Classic CAS

Start on the main screen: Press home to open the Home menu (Calculator, Graphs, Settings, and more). Choose Calculator, or press esc to go back to the calculation page.

  1. Type 90 and add the degree sign (ctrl then the decimal point key).

    90ctrl°.

  2. Press enter. In radian mode the exact answer is π/2.

    enter

You should seeπ/2

Classic CAS key reference

RPN Scientific 15

Start on the main screen: There is no menu to leave. Press the back arrow to clear a number you are typing, or CLx (g then back arrow) to clear the X register.

  1. Key in 180, then press f and 3 for →RAD.

    180f→RAD3

You should see3.1416

Press g and 3 for →DEG to go the other way.

RPN Scientific 15 key reference

RPN Advanced 42

Start on the main screen: Press EXIT (once or twice) to close any menu and return to the plain stack view of Y and X.

  1. Key in 180, open the CONVERT menu (shift then 5) and press the second menu key, →RD.

    180⇧CONVERT51/x

You should seex: 3.1416

RPN Advanced 42 key reference

RPN Power 48

Start on the main screen: Press ON to cancel what you are typing, then use the stack view. Open the MODE or VAR menu any time; the stack is always shown above the menu row.

  1. Key in 90 and press ENTER, then press the right shift and TAN to get π. Multiply, then divide by 180.

    90ENTER▶πTAN×180÷

You should see'π/2'

The answer stays exact as π/2. Press the left shift and EVAL if you want a decimal.

RPN Power 48 key reference

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