How do evaluate sin 270 + cos (-180)?

1 Answer
Alan P.
Oct 1, 2015

#sin(270^@)+cos(-180^@) = -2#

Explanation:

At #270^@# for a unit radius circle
#color(white)("XXX")sin(270^@) = ("opposite")/("hypotenuse")#

#color(white)("XXXXXXXXX")=y/sqrt(x^2+y^2)#

#color(white)("XXXXXXXXX")=(-1)/sqrt(0^2+(-1)^2)#

#color(white)("XXXXXXXXXX")=-1#

At #-180^@# for a unit circle
#color(white)("XXX")cos(-180^@) = ("adjacent")/("hypotenuse")#

(arguing similar to above)
#color(white)("XXXXXXXXXX")= -1#

#sin(270^@)+cos(-180^@) = (-1)+(-1) = -2#

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