6.5 Geometric Constructions
1.
a. Given the line through
A and
B and the point
C, locate
D on
AB such that |
AD| = |
AC| . Then locate
E such that |
CE| = |
DE|. The line through
C and
E is parallel to
AB (
ACED is a parallelogram).

2.
a. The line through (
a,
b) and (
c,
d) has equation
c. Given ax + by = c and dx + ey = f in F[x], the solution (if any) involves only field operations in F, and so both x and y are in F (if they exist).
3. The question asks whether

can be constructed. This is the result of bisecting

. But the angle
π/6 is constructible because

is constructible (see diagram) so angle
π/12 is constructible.
5. No. A sphere of radius 1 has volume

and, if this is the volume of a cube with side a, then . But
a is not constructible since it is not even algebraic over . For if ...