There are an infinite number of triangles that must be isosceles and have two legs that measure 10 cm, each of them has an area. what is the biggest area such a triangle could have?
area=1/2 b*h
b=10cm h=10/2 sinTheta where theta is the angle between the two legs.
area'=1/2 d (bh)/dtheta=1/2 b *cosTheta
set area' to zero, then theta is 90 deg, so find largest area.