Question 276591
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You want an angle in Quadrant II, III, or IV that has the same value of the sine function as an angle of 77 degrees.


First of all, we can eliminate anything in the interval *[tex \LARGE \pi\ \leq\ T\ \leq\ 2\pi], which is to say Quadrants III and IV because the value of the sine function for any angle in Quadrant I, the location of the given 77° angle, is positive, whereas the value of the sine function in Quadrants III and IV is negative.  That means that the angle we are looking for must be in Quadrant II.


The value of the sine function for any angle *[tex \LARGE \theta] is the *[tex \LARGE y]-coordinate of the point of intersection with the terminal side ray of the angle and the unit circle.


Hence the angle needed is 180° - 77° = 103°


<img src="http://www.math.ucsd.edu/~jarmel/math4c/Unit_Circle_Angles.png">


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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