6(x-7)=10(x+4)
6x-42=10x+40
-42-40=10x-6x
-82=4x
x=-20.5 done.
The measurement of fourth angle is: 130°
Further explanation:
Let A, B, C and D be the four angles.
m∠A=105°
m∠B=80°
m∠C=45°
We know that the sum of interior angles of a quadrilateral is 360°
So,
m∠A+m∠B+m∠C+m∠D=360°
105°+80°+45°+m∠D=360°
230°+m∠D=360°
m∠D=360°-230°
m∠D=130°
The measurement of fourth angle is: 130°
Keywords: Quadrilateral, Interior angles
Learn more about quadrilateral at:
#LearnwithBrainly
This question is solved applying the formula of the area of the rectangle, and finding it's width. To do this, we solve a quadratic equation, and we get that the cardboard has a width of 1.5 feet.
Area of a rectangle:
The area of rectangle of length l and width w is given by:

w(2w + 3) = 9
From this, we get that:

Solving a quadratic equation:
Given a second order polynomial expressed by the following equation:
.
This polynomial has roots
such that
, given by the following formulas:
In this question:


Thus a quadratic equation with 
Then


Width is a positive measure, thus, the width of the cardboard is of 1.5 feet.
Another similar problem can be found at brainly.com/question/16995958
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. 
In the figure, tx is perpendicular to line RS.this means we can use the pythagorean theorem to determine RX length the long way or simply apply the theorem that each divided triangle becomes a 30-60-90 angle. If opposite to 60 deg is equal to 6 units, then the side's length is equal to 2*6/sq rt 3 or equal to 6.93 units. The answer is half of this equal to 3.47 units.