Question #7a8d5

1 Answer
Somebody N.
Dec 15, 2017

#(2sqrt(5))/5#

Explanation:

Identities:

#color(red)(1+cot^2x=csc^2x)#

#color(red)(csc^2x=1/sin^2x#

#color(red)(cotx=1/tanx#

................................................................................................................................
#tanx=-2# , #cotx=-1/2#, #cot^2x=1/4#

#1/sin^2x=1/4+1=5/4#

#sin^2x=4/5#

#sinx=sqrt(4/5)=2/sqrt(5)=(2sqrt(5))/5#

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