If triangle ABC is right angled at C, then the value of cos (A + B) is
(a) 0
(b) 1
(c) 1/2
(d) √3/2
Answer :
since ABC is right angled and angle C is 90°
therefore,
A+B=180° – C
A+B=180°-90°
A+B= 90°
Hence, cos (A+B)=cos90°
=0
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