Evaluate square root of 2sin((3pi)/8)cos((3pi)/8)

$\sqrt{2} \sin (\frac{3 π}{8}) \cos (\frac{3 π}{8})$

Step 1

The exact value of $\sin (\frac{3 π}{8})$ is $\frac{\sqrt{2 + \sqrt{2}}}{2}$ .

Rewrite $\frac{3 π}{8}$ as an angle where the values of the six trigonometric functions are known divided by $2$ .

$\sqrt{2} \sin (\frac{\frac{3 π}{4}}{2}) \cos (\frac{3 π}{8})$

Apply the sine half-angle identity.

$\sqrt{2} (\pm \sqrt{\frac{1 - \cos (\frac{3 π}{4})}{2}}) \cos (\frac{3 π}{8})$

Change the $\pm$ to $+$ because sine is positive in the first quadrant.

$\sqrt{2} \sqrt{\frac{1 - \cos (\frac{3 π}{4})}{2}} \cos (\frac{3 π}{8})$

Simplify $\sqrt{\frac{1 - \cos (\frac{3 π}{4})}{2}}$ .

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.

$\sqrt{2} \sqrt{\frac{1 - - \cos (\frac{π}{4})}{2}} \cos (\frac{3 π}{8})$

The exact value of $\cos (\frac{π}{4})$ is $\frac{\sqrt{2}}{2}$ .

$\sqrt{2} \sqrt{\frac{1 - - \frac{\sqrt{2}}{2}}{2}} \cos (\frac{3 π}{8})$

Multiply $- - \frac{\sqrt{2}}{2}$ .

Multiply $- 1$ by $- 1$ .

$\sqrt{2} \sqrt{\frac{1 + 1 \frac{\sqrt{2}}{2}}{2}} \cos (\frac{3 π}{8})$

Multiply $\frac{\sqrt{2}}{2}$ by $1$ .

$\sqrt{2} \sqrt{\frac{1 + \frac{\sqrt{2}}{2}}{2}} \cos (\frac{3 π}{8})$

Write $1$ as a fraction with a common denominator.

$\sqrt{2} \sqrt{\frac{\frac{2}{2} + \frac{\sqrt{2}}{2}}{2}} \cos (\frac{3 π}{8})$

Combine the numerators over the common denominator.

$\sqrt{2} \sqrt{\frac{\frac{2 + \sqrt{2}}{2}}{2}} \cos (\frac{3 π}{8})$

Multiply the numerator by the reciprocal of the denominator.

$\sqrt{2} \sqrt{\frac{2 + \sqrt{2}}{2} \cdot \frac{1}{2}} \cos (\frac{3 π}{8})$

Multiply $\frac{2 + \sqrt{2}}{2} \cdot \frac{1}{2}$ .

Multiply $\frac{2 + \sqrt{2}}{2}$ by $\frac{1}{2}$ .

$\sqrt{2} \sqrt{\frac{2 + \sqrt{2}}{2 \cdot 2}} \cos (\frac{3 π}{8})$

Multiply $2$ by $2$ .

$\sqrt{2} \sqrt{\frac{2 + \sqrt{2}}{4}} \cos (\frac{3 π}{8})$

Rewrite $\sqrt{\frac{2 + \sqrt{2}}{4}}$ as $\frac{\sqrt{2 + \sqrt{2}}}{\sqrt{4}}$ .

$\sqrt{2} \frac{\sqrt{2 + \sqrt{2}}}{\sqrt{4}} \cos (\frac{3 π}{8})$

Simplify the denominator.

Rewrite $4$ as $2^{2}$ .

$\sqrt{2} \frac{\sqrt{2 + \sqrt{2}}}{\sqrt{2^{2}}} \cos (\frac{3 π}{8})$

Pull terms out from under the radical, assuming positive real numbers.

$\sqrt{2} \frac{\sqrt{2 + \sqrt{2}}}{2} \cos (\frac{3 π}{8})$

Step 2

Multiply $\sqrt{2} \frac{\sqrt{2 + \sqrt{2}}}{2}$ .

Combine $\sqrt{2}$ and $\frac{\sqrt{2 + \sqrt{2}}}{2}$ .

$\frac{\sqrt{2} \sqrt{2 + \sqrt{2}}}{2} \cos (\frac{3 π}{8})$

Combine using the product rule for radicals.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \cos (\frac{3 π}{8})$

Step 3

The exact value of $\cos (\frac{3 π}{8})$ is $\frac{\sqrt{2 - \sqrt{2}}}{2}$ .

Rewrite $\frac{3 π}{8}$ as an angle where the values of the six trigonometric functions are known divided by $2$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \cos (\frac{\frac{3 π}{4}}{2})$

Apply the cosine half-angle identity $\cos (\frac{x}{2}) = \pm \sqrt{\frac{1 + \cos (x)}{2}}$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} (\pm \sqrt{\frac{1 + \cos (\frac{3 π}{4})}{2}})$

Change the $\pm$ to $+$ because cosine is positive in the first quadrant.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{1 + \cos (\frac{3 π}{4})}{2}}$

Simplify $\sqrt{\frac{1 + \cos (\frac{3 π}{4})}{2}}$ .

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{1 - \cos (\frac{π}{4})}{2}}$

The exact value of $\cos (\frac{π}{4})$ is $\frac{\sqrt{2}}{2}$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{1 - \frac{\sqrt{2}}{2}}{2}}$

Write $1$ as a fraction with a common denominator.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{\frac{2}{2} - \frac{\sqrt{2}}{2}}{2}}$

Combine the numerators over the common denominator.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{\frac{2 - \sqrt{2}}{2}}{2}}$

Multiply the numerator by the reciprocal of the denominator.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{2 - \sqrt{2}}{2} \cdot \frac{1}{2}}$

Multiply $\frac{2 - \sqrt{2}}{2} \cdot \frac{1}{2}$ .

Multiply $\frac{2 - \sqrt{2}}{2}$ by $\frac{1}{2}$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{2 - \sqrt{2}}{2 \cdot 2}}$

Multiply $2$ by $2$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \sqrt{\frac{2 - \sqrt{2}}{4}}$

Rewrite $\sqrt{\frac{2 - \sqrt{2}}{4}}$ as $\frac{\sqrt{2 - \sqrt{2}}}{\sqrt{4}}$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \cdot \frac{\sqrt{2 - \sqrt{2}}}{\sqrt{4}}$

Simplify the denominator.

Rewrite $4$ as $2^{2}$ .

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \cdot \frac{\sqrt{2 - \sqrt{2}}}{\sqrt{2^{2}}}$

Pull terms out from under the radical, assuming positive real numbers.

$\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \cdot \frac{\sqrt{2 - \sqrt{2}}}{2}$

Step 4

Multiply $\frac{\sqrt{2 (2 + \sqrt{2})}}{2} \cdot \frac{\sqrt{2 - \sqrt{2}}}{2}$ .

Multiply $\frac{\sqrt{2 (2 + \sqrt{2})}}{2}$ by $\frac{\sqrt{2 - \sqrt{2}}}{2}$ .

$\frac{\sqrt{2 (2 + \sqrt{2})} \sqrt{2 - \sqrt{2}}}{2 \cdot 2}$

Combine using the product rule for radicals.

$\frac{\sqrt{2 (2 + \sqrt{2}) (2 - \sqrt{2})}}{2 \cdot 2}$

Apply the distributive property.

$\frac{\sqrt{(2 \cdot 2 + 2 \sqrt{2}) (2 - \sqrt{2})}}{2 \cdot 2}$

Multiply $2$ by $2$ .

$\frac{\sqrt{(4 + 2 \sqrt{2}) (2 - \sqrt{2})}}{2 \cdot 2}$

Expand $(4 + 2 \sqrt{2}) (2 - \sqrt{2})$ using the FOIL Method.

Apply the distributive property.

$\frac{\sqrt{4 (2 - \sqrt{2}) + 2 \sqrt{2} (2 - \sqrt{2})}}{2 \cdot 2}$

Apply the distributive property.

$\frac{\sqrt{4 \cdot 2 + 4 (- \sqrt{2}) + 2 \sqrt{2} (2 - \sqrt{2})}}{2 \cdot 2}$

Apply the distributive property.

$\frac{\sqrt{4 \cdot 2 + 4 (- \sqrt{2}) + 2 \sqrt{2} \cdot 2 + 2 \sqrt{2} (- \sqrt{2})}}{2 \cdot 2}$

Simplify and combine like terms.

Simplify each term.

Multiply $4$ by $2$ .

$\frac{\sqrt{8 + 4 (- \sqrt{2}) + 2 \sqrt{2} \cdot 2 + 2 \sqrt{2} (- \sqrt{2})}}{2 \cdot 2}$

Multiply $- 1$ by $4$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 2 \sqrt{2} \cdot 2 + 2 \sqrt{2} (- \sqrt{2})}}{2 \cdot 2}$

Multiply $2$ by $2$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} + 2 \sqrt{2} (- \sqrt{2})}}{2 \cdot 2}$

Multiply $2 \sqrt{2} (- \sqrt{2})$ .

Multiply $- 1$ by $2$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 \sqrt{2} \sqrt{2}}}{2 \cdot 2}$

Raise $\sqrt{2}$ to the power of $1$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 ({\sqrt{2}}^{1} \sqrt{2})}}{2 \cdot 2}$

Raise $\sqrt{2}$ to the power of $1$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 ({\sqrt{2}}^{1} {\sqrt{2}}^{1})}}{2 \cdot 2}$

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 {\sqrt{2}}^{1 + 1}}}{2 \cdot 2}$

Add $1$ and $1$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 {\sqrt{2}}^{2}}}{2 \cdot 2}$

Rewrite ${\sqrt{2}}^{2}$ as $2$ .

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{2}$ as $2^{\frac{1}{2}}$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 {(2^{\frac{1}{2}})}^{2}}}{2 \cdot 2}$

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 \cdot 2^{\frac{1}{2} \cdot 2}}}{2 \cdot 2}$

Combine $\frac{1}{2}$ and $2$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 \cdot 2^{\frac{2}{2}}}}{2 \cdot 2}$

Cancel the common factor of $2$ .

Cancel the common factor.

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 \cdot 2^{\frac{2}{2}}}}{2 \cdot 2}$

Rewrite the expression.

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 \cdot 2^{1}}}{2 \cdot 2}$

Evaluate the exponent.

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 2 \cdot 2}}{2 \cdot 2}$

Multiply $- 2$ by $2$ .

$\frac{\sqrt{8 - 4 \sqrt{2} + 4 \sqrt{2} - 4}}{2 \cdot 2}$

Subtract $4$ from $8$ .

$\frac{\sqrt{4 - 4 \sqrt{2} + 4 \sqrt{2}}}{2 \cdot 2}$

Add $- 4 \sqrt{2}$ and $4 \sqrt{2}$ .

$\frac{\sqrt{4 + 0}}{2 \cdot 2}$

Add $4$ and $0$ .

$\frac{\sqrt{4}}{2 \cdot 2}$

Multiply $2$ by $2$ .

$\frac{\sqrt{4}}{4}$

Step 5

Simplify the numerator.

Rewrite $4$ as $2^{2}$ .

$\frac{\sqrt{2^{2}}}{4}$

Pull terms out from under the radical, assuming positive real numbers.

$\frac{2}{4}$

Step 6

Cancel the common factor of $2$ and $4$ .

Factor $2$ out of $2$ .

$\frac{2 (1)}{4}$

Cancel the common factors.

Factor $2$ out of $4$ .

$\frac{2 \cdot 1}{2 \cdot 2}$

Cancel the common factor.

$\frac{2 \cdot 1}{2 \cdot 2}$

Rewrite the expression.

$\frac{1}{2}$

Step 7

The result can be shown in multiple forms.

Exact Form:

$\frac{1}{2}$

Decimal Form:

$0.5$

Evaluate square root of 2sin((3pi)/8)cos((3pi)/8)

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