Trigonometry Examples

Solve for x cos(2x)+5sin(x)=-2
Step 1
Add to both sides of the equation.
Step 2
Simplify the left side of the equation.
Tap for more steps...
Step 2.1
Use the double-angle identity to transform to .
Step 2.2
Add and .
Step 3
Factor by grouping.
Tap for more steps...
Step 3.1
Reorder terms.
Step 3.2
For a polynomial of the form , rewrite the middle term as a sum of two terms whose product is and whose sum is .
Tap for more steps...
Step 3.2.1
Factor out of .
Step 3.2.2
Rewrite as plus
Step 3.2.3
Apply the distributive property.
Step 3.3
Factor out the greatest common factor from each group.
Tap for more steps...
Step 3.3.1
Group the first two terms and the last two terms.
Step 3.3.2
Factor out the greatest common factor (GCF) from each group.
Step 3.4
Factor the polynomial by factoring out the greatest common factor, .
Step 4
If any individual factor on the left side of the equation is equal to , the entire expression will be equal to .
Step 5
Set equal to and solve for .
Tap for more steps...
Step 5.1
Set equal to .
Step 5.2
Solve for .
Tap for more steps...
Step 5.2.1
Add to both sides of the equation.
Step 5.2.2
Divide each term in by and simplify.
Tap for more steps...
Step 5.2.2.1
Divide each term in by .
Step 5.2.2.2
Simplify the left side.
Tap for more steps...
Step 5.2.2.2.1
Cancel the common factor of .
Tap for more steps...
Step 5.2.2.2.1.1
Cancel the common factor.
Step 5.2.2.2.1.2
Divide by .
Step 5.2.2.3
Simplify the right side.
Tap for more steps...
Step 5.2.2.3.1
Move the negative in front of the fraction.
Step 5.2.3
Take the inverse sine of both sides of the equation to extract from inside the sine.
Step 5.2.4
Simplify the right side.
Tap for more steps...
Step 5.2.4.1
The exact value of is .
Step 5.2.5
The sine function is negative in the third and fourth quadrants. To find the second solution, subtract the solution from , to find a reference angle. Next, add this reference angle to to find the solution in the third quadrant.
Step 5.2.6
Simplify the expression to find the second solution.
Tap for more steps...
Step 5.2.6.1
Subtract from .
Step 5.2.6.2
The resulting angle of is positive, less than , and coterminal with .
Step 5.2.7
Find the period of .
Tap for more steps...
Step 5.2.7.1
The period of the function can be calculated using .
Step 5.2.7.2
Replace with in the formula for period.
Step 5.2.7.3
The absolute value is the distance between a number and zero. The distance between and is .
Step 5.2.7.4
Divide by .
Step 5.2.8
Add to every negative angle to get positive angles.
Tap for more steps...
Step 5.2.8.1
Add to to find the positive angle.
Step 5.2.8.2
To write as a fraction with a common denominator, multiply by .
Step 5.2.8.3
Combine fractions.
Tap for more steps...
Step 5.2.8.3.1
Combine and .
Step 5.2.8.3.2
Combine the numerators over the common denominator.
Step 5.2.8.4
Simplify the numerator.
Tap for more steps...
Step 5.2.8.4.1
Multiply by .
Step 5.2.8.4.2
Subtract from .
Step 5.2.8.5
List the new angles.
Step 5.2.9
The period of the function is so values will repeat every radians in both directions.
, for any integer
, for any integer
, for any integer
Step 6
Set equal to and solve for .
Tap for more steps...
Step 6.1
Set equal to .
Step 6.2
Solve for .
Tap for more steps...
Step 6.2.1
Add to both sides of the equation.
Step 6.2.2
The range of sine is . Since does not fall in this range, there is no solution.
No solution
No solution
No solution
Step 7
The final solution is all the values that make true.
, for any integer