Question about Texas Instruments TI-84 Plus Calculator

# How do I calculate the ArcCos of say -.25? When I use the TI-84 Plus Silver Edition I first press 2nd the Cos to obtain Cos-1. I then put in -.25 and close parenthesis ) and then enter. The value I get is 1.8234...., however, the value should be 104.478 degrees. What am I doing wrong.

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• Texas Instru... Master

Hello,
There is nothing wrong. Your angle unit is set to radians and the calculator gave you the correct angle the cosine of which is -0.25: the answer is in the same unit as the one your calculator is configured for.
Press [MODE]. Use arrow to scroll to 3rd line, highlight Degree and press [ENTER]. Press [2nd][QUIT] to return to main calculator screen.
As long as the angle unit is set to degree, the angles calculated by the inverse trigonometric function will be in degrees.

Hope it helps.

Posted on Nov 14, 2009

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Posted on Jan 02, 2017

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