Here's one approach:
Without loss of generality let AB = 1
Angle ADB = 180-80-50 = 50 so triangle ABD is isosceles and AD = AB = 1
Angle AEB = 180-60-80 = 40, so AE/sin(80) = 1/sin(40) or AE = sin(80)/sin(40)
Angle BDE = 180-30-(40+x) = 110-x
Angle ADE = ADB + BDE = 50 + 110 - x = 160 - x
Sine rule on triangle ADE:
sin(x)/AD = sin(160-x)/AE or sin(x)/1 = sin(160-x)*sin(40)/sin(80)
Rearrange: sin(80)*sin(x) = sin(40)*sin(160-x)
sin(80)*sin(x) = sin(40)*(sin(160)*cos(x) - cos(160)*sin(x))
I'm sure you can take it from here (collect sin(x) terms on one side, cos(x) on the other, divide to get tan( x) ...etc.)
As Guest #1 notes, you should find x = 30 degrees.
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In this equation, your eventual goal is to isolate y. Let's see how to do this:
\(y-1-2y=y+1-3y\) | Simplify both sides of the equation by combining like terms. In this case, the linear terms can be combined to simplify things |
\(-y-1=-2y+1\) | Add y to both sides of the equation. Doing this will have a y that will cancel on the left hand side. |
\(-1=-y+1\) | Subtract 1 from both sides |
\(-2=-y\) | Divide by -1 to get rid of the negative sign on the y. |
\(2=y\) | |
If you are ever pondering about whether or not this answer is correct, plug the answer you got into your equation and see if the statement is true. :
\(y-1-2y=y+1-3y\) | Replace all instances of a y with a 2 |
\(2-1-2*2=2+1-3*2\) | Simplify and see if the statement is true |
\(2-1-4=2+1-6\) | |
\(1-4=3-6\) | |
\(-3=-3\) | Indeed, this is a true statement. |
Therefore, \(y=2\) is the correct and only correct solution for the given equation
Are there any requirements or guidelines that the function has to have?
If there aren't any, here's a simple one....
function: y = (4/5)x , x ≥ 0
real life situation: It costs $4.00 to buy 5 apples. What is the price for any number of apples ?
x (input) = number of apples
y (output) = total price
table:
___x,__ number of apples___ | ___y,__ price in dollars___ |
---|---|
1 | 0.80 |
2 | 1.60 |
3 | 2.40 |
4 | 3.20 |
5 | 4.00 |
graph: http://www.desmos.com/calculator/qsmzdsxcsu
domain: all real numbers ≥ 0
range: all real numbers ≥ 0
Does your function have a positive or negative slope? Why?
It has a positive slope because the more apples you buy, the higher the price.
What is the relationship between your input and output?
y is directly proportional to x.