Randolph College
Department of Mathematics and Computer Science

 

Homework # 3 - Math 250


The problems on this homework must be done alone.  The honor code is in effect.

 First name:   Last name:


 

In questions 1, 2, and 3 consider the triangle with vertices A(1,2,3), B(5,5,3), and C(3,4,4).

1.  Find cos\(\theta\) where \(\theta\) is the smallest angle in the triangle.

a.  -14/15

b.  -1/15

c.  0

d.  1/15

e.  14/15

2.  Classify this triangle as one of the following.

a.  Acute

b.  Right

c.  Obtuse

3.  Find the coordinates of D so that ABCD is a parallogram. Hint: this means that opposite sides must be parallel.

a.  (7, 7, 4)

b.  (3, 3, 2)

c.  (-1, 1, 4)

d.  (0, 0 ,0)

e.  (7, 8, 3)

4.  For how many different values of t would the vectors 〈t, t, -1〉,〈t, 1, 6〉 be orthogonal?

a.  None

b.  One

c.  Two

d.  Three

e.  Infinitely many

 

5.  Find the area of parallelogram ABCD.

a.  9√3/2

b.  6√3

c.  15√3/2

d.  9√3

e.  21√3/2

6.  Find the area of triangle ABC.

a.  9√3/2

b.  6√3

c.  15√3/2

d.  9√3

e.  21√3/2