Answer:
B- Parallelogram PQRS is also a rhombus.
Step-by-step explanation:
Given
Parallelogram PQRS with perpendicular diagonals
Required
Which of the option is true
(a) PQRS can be a rectangle
A rectangle do not have perpendicular diagonals.
Hence, (a) is false
<em>If (a) is false, then (d) is also false</em>
(b) PQRS can a rhombus
The diagonals of a rhombus are not perpendicular.
So (b) <em>is true</em>
<em>No need to check for (c), since only option is true</em>
Step 
<u>Find the length of the side MN</u>
we know that
Applying the Pythagorean Theorem
Solve for MN
in this problem
Substitute in the formula above
Step 
<u>Find the value of cos (M)</u>
we know that
in the right triangle MNL
Substitute
therefore
The answer is
The value of cos(M) is equal to 
To solve this problem you must apply the proccedure shown below:
1. You have the following expression:
(3+3i)-(13+15i)
2. If you want to substract both terms, you need to substract the real numbers and the complex numbers. Then, you obtain:
3+3i-13-15i
(3-13)+(3i-15i)
3. Then, you obtain the following result:
-10-12i
4. Therefore, as you can see, the correct answer is the last option (option D), which is:
D. -10-12i
Step-by-step explanation:
C4H6O3 + H2O => 2C2H4O2
C2H4 + 3O2 => 2CO2 + 2H2O
C4H10O + 6O2 => 4CO2 + 5H2O
