is in quadrant I, so
.
is in quadrant II, so
.
Recall that for any angle
,

Then with the conditions determined above, we get

and

Now recall the compound angle formulas:




as well as the definition of tangent:

Then
1. 
2. 
3. 
4. 
5. 
6. 
7. A bit more work required here. Recall the half-angle identities:



Because
is in quadrant II, we know that
is in quadrant I. Specifically, we know
, so
. In this quadrant, we have
, so

8. 
Let n = minutes since 12:00 pm when Malory catches up to Dori.
Dori travels
(50 steps/min)*(n minutes) = 50n steps
Malory begins walking at 12:20 pm, so she walks for (n - 20) minutes. She travels
(90 steps/min)*(n - 20 min) = 90n - 1800 steps
Equate the steps traveled by Dori and Malory.
90n - 1800 = 50n
40n = 1800
n = 45 min
The time corresponding to n = 45 min is 12:45 pm
Answer: 12:45 pm
If the length is 7/6 the width w then the perimeter is w + (7/6)w + w + (7/6w)
= 2((7/6)w + w) = 2w + (14/6)w = (26/6)w = (13/3)w.
So the answer is the last one.