Given point (12,-9) how do you find the distance of the point from the origin, then find the measure of the angle in standard position whose terminal side contains the point?

1 Answer
Vinícius Ferraz
Dec 27, 2016

#r = 15, angle xOP = 2 pi - arctan frac{3}{4}#

Explanation:

The old and good formulas.

#x = r cos t = 12#
#y = r sin t = -9#

#x^2 + y^2 = r^2 = 144 + 81 = 225#
#r = 15#

#y / x = tan t = -9/12 = -3/4#

#t = - arctan 0.75#

#tan(-theta) = - tan theta = tan (2 pi - theta)#

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