how cos 3pi/4 equals -1/root 2?

incomplex numbers cos 3pi/4 equals -1/root2?how?
in Trigonometry Answers by Level 1 User (120 points)

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1 Answer

(3/4)pi=3/4)*180 deg=135 deg=-0.7071067811865475=(1/2)*sqrt(2)

kosine(0)=1 & go down tu 0 at 90 deg, & down tu -1 at 180 deg

135=90+45 deg, half wae tween 90 & 180

kosine(135 deg)=-kosine(45 deg)

me spekt teech alredee giv yu kosine(45)
by

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