Trigonometry Examples

$\cot (x) \sec (x) = 2 \cot (x)$

Step 1

Simplify the left side.

Tap for more steps...

Step 1.1

Rewrite in terms of sines and cosines, then cancel the common factors.

Tap for more steps...

Step 1.1.1

Rewrite $\cot (x) \sec (x)$ in terms of sines and cosines.

$\frac{\cos (x)}{\sin (x)} \cdot \frac{1}{\cos (x)} = 2 \cot (x)$

Step 1.1.2

Cancel the common factors.

$\frac{1}{\sin (x)} = 2 \cot (x)$

Step 2

Simplify the right side.

Tap for more steps...

Step 2.1

Simplify $2 \cot (x)$ .

Tap for more steps...

Step 2.1.1

Rewrite $\cot (x)$ in terms of sines and cosines.

$\frac{1}{\sin (x)} = 2 \frac{\cos (x)}{\sin (x)}$

Step 2.1.2

Combine $2$ and $\frac{\cos (x)}{\sin (x)}$ .

$\frac{1}{\sin (x)} = \frac{2 \cos (x)}{\sin (x)}$

Step 3

Multiply both sides of the equation by $\sin (x)$ .

$\sin (x) \frac{1}{\sin (x)} = \sin (x) \frac{2 \cos (x)}{\sin (x)}$

Step 4

Cancel the common factor of $\sin (x)$ .

Tap for more steps...

Step 4.1

Cancel the common factor.

$\sin (x) \frac{1}{\sin (x)} = \sin (x) \frac{2 \cos (x)}{\sin (x)}$

Step 4.2

Rewrite the expression.

$1 = \sin (x) \frac{2 \cos (x)}{\sin (x)}$

Step 5

Cancel the common factor of $\sin (x)$ .

Tap for more steps...

Step 5.1

Cancel the common factor.

$1 = \sin (x) \frac{2 \cos (x)}{\sin (x)}$

Step 5.2

Rewrite the expression.

$1 = 2 \cos (x)$

Step 6

Rewrite the equation as $2 \cos (x) = 1$ .

$2 \cos (x) = 1$

Step 7

Divide each term in $2 \cos (x) = 1$ by $2$ and simplify.

Tap for more steps...

Step 7.1

Divide each term in $2 \cos (x) = 1$ by $2$ .

$\frac{2 \cos (x)}{2} = \frac{1}{2}$

Step 7.2

Simplify the left side.

Tap for more steps...

Step 7.2.1

Cancel the common factor of $2$ .

Tap for more steps...

Step 7.2.1.1

Cancel the common factor.

$\frac{2 \cos (x)}{2} = \frac{1}{2}$

Step 7.2.1.2

Divide $\cos (x)$ by $1$ .

$\cos (x) = \frac{1}{2}$

Step 8

Take the inverse cosine of both sides of the equation to extract $x$ from inside the cosine.

$x = \arccos (\frac{1}{2})$

Step 9

Simplify the right side.

Tap for more steps...

Step 9.1

The exact value of $\arccos (\frac{1}{2})$ is $\frac{π}{3}$ .

$x = \frac{π}{3}$

Step 10

The cosine function is positive in the first and fourth quadrants. To find the second solution, subtract the reference angle from $2 π$ to find the solution in the fourth quadrant.

$x = 2 π - \frac{π}{3}$

Step 11

Simplify $2 π - \frac{π}{3}$ .

Tap for more steps...

Step 11.1

To write $2 π$ as a fraction with a common denominator, multiply by $\frac{3}{3}$ .

$x = 2 π \cdot \frac{3}{3} - \frac{π}{3}$

Step 11.2

Combine fractions.

Tap for more steps...

Step 11.2.1

Combine $2 π$ and $\frac{3}{3}$ .

$x = \frac{2 π \cdot 3}{3} - \frac{π}{3}$

Step 11.2.2

Combine the numerators over the common denominator.

$x = \frac{2 π \cdot 3 - π}{3}$

Step 11.3

Simplify the numerator.

Tap for more steps...

Step 11.3.1

Multiply $3$ by $2$ .

$x = \frac{6 π - π}{3}$

Step 11.3.2

Subtract $π$ from $6 π$ .

$x = \frac{5 π}{3}$

Step 12

Find the period of $\cos (x)$ .

Tap for more steps...

Step 12.1

The period of the function can be calculated using $\frac{2 π}{| b |}$ .

$\frac{2 π}{| b |}$

Step 12.2

Replace $b$ with $1$ in the formula for period.

$\frac{2 π}{| 1 |}$

Step 12.3

The absolute value is the distance between a number and zero. The distance between $0$ and $1$ is $1$ .

$\frac{2 π}{1}$

Step 12.4

Divide $2 π$ by $1$ .

$2 π$

Step 13

The period of the $\cos (x)$ function is $2 π$ so values will repeat every $2 π$ radians in both directions.

$x = \frac{π}{3} + 2 π n, \frac{5 π}{3} + 2 π n$ , for any integer $n$