Examples with solutions for Square of sum: Using Pythagoras' theorem

Exercise #1

Calculate x according to the figure shown below below.

x>0 x>0

x+1x+1x+1xxxx+2x+2x+2

Video Solution

Step-by-Step Solution

To find x x in the given triangle, let's apply the Pythagorean Theorem. The squared lengths of the triangle's legs and hypotenuse are related by this equation:

(x+1)2+x2=(x+2)2 (x+1)^2 + x^2 = (x+2)^2

First, expand each term:

  • (x+1)2=x2+2x+1 (x+1)^2 = x^2 + 2x + 1
  • x2=x2 x^2 = x^2
  • (x+2)2=x2+4x+4 (x+2)^2 = x^2 + 4x + 4

Plug these into the Pythagorean Theorem equation:

(x2+2x+1)+x2=x2+4x+4 (x^2 + 2x + 1) + x^2 = x^2 + 4x + 4

Combine like terms:

2x2+2x+1=x2+4x+4 2x^2 + 2x + 1 = x^2 + 4x + 4

Rearrange the equation to isolate terms on one side:

2x2+2x+1x24x4=0 2x^2 + 2x + 1 - x^2 - 4x - 4 = 0

Simplify to get a quadratic equation:

x22x3=0 x^2 - 2x - 3 = 0

Now, solve for x x using factoring. Look for two numbers that multiply to 3-3 and add to 2-2. These numbers are 3-3 and 11:

(x3)(x+1)=0 (x - 3)(x + 1) = 0

Set each factor equal to zero:

  • x3=0x=3 x - 3 = 0 \Rightarrow x = 3
  • x+1=0x=1 x + 1 = 0 \Rightarrow x = -1

Given the condition x>0 x > 0 , the valid solution is:

x=3 x = 3

Answer

x=3 x=3

Exercise #2

Given a circle whose center O. From the center of the circle go out 2 radii that cut the circle at the points A and B.

Given AO⊥OB.

The side AB is equal to and+2.

Express band and the area of the circle.

y+2y+2y+2AAABBBOOO

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Identify the given information.
  • Use the geometric properties of a circle and a right triangle to find the radius.
  • Express the area of the circle in terms of the given expression.

Now, let's work through each step:

Step 1: Given a circle with center O O and radii AO AO and OB OB such that AOOB AO\perp OB , each is a radius r r , and AB=and+2 AB = \text{and}+2 .

Step 2: By the Pythagorean theorem, we know:

AO2+OB2=AB2 AO^2 + OB^2 = AB^2 r2+r2=(y+2)2 r^2 + r^2 = (y+2)^2 2r2=y2+4y+4 2r^2 = y^2 + 4y + 4

Step 3: Solving for the area of the circle:

The radius r r can be expressed by rearranging:

r2=y2+4y+42 r^2 = \frac{y^2 + 4y + 4}{2}

The area of the circle using this radius is:

Area=πr2=π(y2+4y+42)=π2(y2+4y+4) \text{Area} = \pi r^2 = \pi \left(\frac{y^2 + 4y + 4}{2}\right) = \frac{\pi}{2}(y^2 + 4y + 4)

Therefore, the expression for the area of the circle is π2[y2+4y+4] \frac{\pi}{2}[y^2+4y+4] .

Answer

π2[y2+4y+4] \frac{\pi}{2}[y^2+4y+4]

Exercise #3

The rectangle ABCD is shown below.

AB = X

The ratio between AB and BC is x2 \sqrt{\frac{x}{2}} .


The length of diagonal AC is labelled m.

XXXmmmAAABBBCCCDDD

Determine the value of m:

Video Solution

Step-by-Step Solution

We know that:

ABBC=x2 \frac{AB}{BC}=\sqrt{\frac{x}{2}}

We also know that AB equals X.

First, we will substitute the given data into the formula accordingly:

xBC=x2 \frac{x}{BC}=\frac{\sqrt{x}}{\sqrt{2}}

x2=BCx x\sqrt{2}=BC\sqrt{x}

x2x=BC \frac{x\sqrt{2}}{\sqrt{x}}=BC

x×x×2x=BC \frac{\sqrt{x}\times\sqrt{x}\times\sqrt{2}}{\sqrt{x}}=BC

x×2=BC \sqrt{x}\times\sqrt{2}=BC

Now let's look at triangle ABC and use the Pythagorean theorem:

AB2+BC2=AC2 AB^2+BC^2=AC^2

We substitute in our known values:

x2+(x×2)2=m2 x^2+(\sqrt{x}\times\sqrt{2})^2=m^2

x2+x×2=m2 x^2+x\times2=m^2

Finally, we will add 1 to both sides:

x2+2x+1=m2+1 x^2+2x+1=m^2+1

(x+1)2=m2+1 (x+1)^2=m^2+1

Answer

m2+1=(x+1)2 m^2+1=(x+1)^2