Find the exact value of cos 210º - cot 210º??

1 Answer
Jim G.
Jul 16, 2018

#-(3sqrt3)/2#

Explanation:

#210^@" is in the third quadrant where"#

#cos210^@<0" and "cot210^@>0#

#cos210^@#

#=-cos(210-180)^@#

#=-cos30^@=-sqrt3/2#

#tan210^@=tan(210-180)^@=tan30^@=1/sqrt3#

#rArrcot210^@=1/(tan210^@)=1/(1/sqrt3)=sqrt3#

#"hence"#

#cos210^@-cot210^@#

#=-sqrt3/2-sqrt3=-3/2sqrt3=-(3sqrt3)/2#

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