Question 755553
exact value of sin 255
sin (255)=sin(135+120)=sin135 cos120+cos135 sin120
sin135º=&#8730;2/2*-1/2-&#8730;2/2*&#8730;3/2 =-&#8730;2/4-&#8730;6/4=-(&#8730;2+&#8730;6)/4
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calculator check:
sin255º&#8776;-0.9659..
exact value=-(&#8730;2+&#8730;6)/4&#8776;-0.9659