Hello!
The answer for A is:
The answer for B is: The rocket will hit the lake surface in 5 seconds.
<h2>Why?</h2>
Defining the terms:
So, replacing it in the quadratic equation (it's given to you in the exercise)\\
We are working with a quadratic equation, so we will have two possible results,
Now, we are asked to find the time, time can not be a negative value, we have to discard X1 (-1) since it's a negative value, knowing that, the rocket will hit the lake after 5 seconds.
Have a nice day!
Value of the expression will be 7
<u><em>Explanation</em></u>
Given value of the variables are : 
and 
Given expression: 
So, <u>plugging the values</u> of 
and 
into the above expression, we will get...
So, the value of the expression will be 7.
0, adding it in and then subtracting it out cancels both out
Set up a ratio:
6/11 = x/26
Cross multiply:
11x = 156
Divide both sides by 11:
X = 14.18 feet ( round answer as needed.)
Answer: 10*(cos(pi) + i*sin(pi))
=======================================
Work Shown:
z1 = 1+i is in the form a+bi where a = 1 and b = 1
r = sqrt(a^2+b^2)
r = sqrt(1^2+1^2)
r = sqrt(2)
theta = arctan(b/a)
theta = arctan(1/1)
theta = pi/4
The polar form for z1 is
z1 = r*(cos(theta) + i*sin(theta))
z1 = sqrt(2)*(cos(pi/4)+i*sin(pi/4)
----------------
z2 = -5+5i is in the form a+bi where a = -5 and b = 5
r = sqrt(a^2+b^2)
r = sqrt((-5)^2+5^2)
r = sqrt(50)
r = 5*sqrt(2)
theta = arctan(b/a)
theta = arctan(5/(-5))
theta = 3pi/4
The polar form for z2 is
z2 = r*(cos(theta) + i*sin(theta))
z2 = 5*sqrt(2)*(cos(3pi/4)+i*sin(3pi/4)
----------------
Now use the rule
If
z = a*(cos(b) + i*sin(b)) and w = c*(cos(d)+i*sin(d))
then
z*w = a*c*(cos(b+d)+i*sin(b+d))
We have
a = sqrt(2)
b = pi/4
c = 5*sqrt(2)
d = 3pi/4
So...
z*w = a*c*(cos(b+d)+i*sin(b+d))
z1*z2 = sqrt(2)*5*sqrt(2)*(cos(pi/4+3pi/4)+i*sin(pi/4+3pi/4))
z1*z2 = 10*(cos(4pi/4)+i*sin(4pi/4))
z1*z2 = 10*(cos(pi)+i*sin(pi))
which is the answer in polar form
