Question 813220
If cos x = -1/5, find the value of cos(x+pi)
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sinx=&#8730;(1-cos^2x)=&#8730;(1-1/25)=&#8730;(24/25)=&#8730;24/5
Identity: cos(a+b)=cosa*cosb-sina*sinb
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cos(x+&#960;)=cosx*cos&#960;-sinx*sin&#960;=(-1/5*-1)-(&#8730;24/5*0)=1/5