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#

enter image source here

Related questions
See all questions in Trigonometric Functions of Any Angle
Impact of this question
5731 views around the world
You can reuse this answer
Creative Commons License