Question

if ∆PQR is a right angled triangle with angleR=90°,then the value of cos(P+Q) is​

Answer 1

△PQR is right angled at R then ∠R=90°

cos(P+Q)=cos(180−R) (Since sum of the angle in a triangle is 180)

⇒cos(P+Q)=cos(180−90)

⇒cos(P+Q)=cos90°

∵cos90°=0

∴cos(P+Q)=0