In a △ABC, if sinAsinB=abc2, then the triangle is
Equilateral
Isosceles
Right-angled
Obtuse-angle
Determine the type of triangle.
We have, sinAsinB=abc2
⇒c2=absinAsinB⇒c2=asinAbsinB...(1)
From sine rule we know that asinA=bsinB=csinC, therefore substitute csinC in equation (1)
⇒c2=c2sin2C⇒sin2C=1⇒sinC=sin90°⇒C=90°
Thus, the triangle is right-angled triangle.
Hence, (C) option is correct.
Evaluate :cos48°-sin42°