Question

If abc is a triangle right angled at c then cos(a+b) is equal to

Answer 1

Answer:

a+b+c=180(sum of all angles of a triangle is 180°)

a+b=180-c

cos(a+b)=cos(180-c)

cos(a+b)=cos(180-90)

cos(a+b)=cos 90

cos(a+b)=0