Question
Solve the equation
x=4π+2kπ,k∈Z
Alternative Form
x=45∘+90∘k,k∈Z
Alternative Form
x≈0.785398+2kπ,k∈Z
Evaluate
8sin2(x)=8cos2(x)
Use sin2(x)=1−cos2(x) to rewrite the expression
8−8cos2(x)=8cos2(x)
Move the expression to the left side
8−8cos2(x)−8cos2(x)=0
Calculate
More Steps

Evaluate
−8cos2(x)−8cos2(x)
Collect like terms by calculating the sum or difference of their coefficients
(−8−8)cos2(x)
Subtract the numbers
−16cos2(x)
8−16cos2(x)=0
Add or subtract both sides
−16cos2(x)=−8
Divide both sides
−16−16cos2(x)=−16−8
Divide the numbers
cos2(x)=21
Take the root of both sides of the equation and remember to use both positive and negative roots
cos(x)=±21
Simplify the expression
cos(x)=±22
Separate the equation into 2 possible cases
cos(x)=22cos(x)=−22
Calculate
More Steps

Evaluate
cos(x)=22
Use the inverse trigonometric function
x=arccos(22)
Calculate
x=4πx=47π
Add the period of 2kπ,k∈Z to find all solutions
x=4π+2kπ,k∈Zx=47π+2kπ,k∈Z
Find the union
x={4π+2kπ47π+2kπ,k∈Z
x={4π+2kπ47π+2kπ,k∈Zcos(x)=−22
Calculate
More Steps

Evaluate
cos(x)=−22
Use the inverse trigonometric function
x=arccos(−22)
Calculate
x=43πx=45π
Add the period of 2kπ,k∈Z to find all solutions
x=43π+2kπ,k∈Zx=45π+2kπ,k∈Z
Find the union
x={43π+2kπ45π+2kπ,k∈Z
x={4π+2kπ47π+2kπ,k∈Zx={43π+2kπ45π+2kπ,k∈Z
Solution
x=4π+2kπ,k∈Z
Alternative Form
x=45∘+90∘k,k∈Z
Alternative Form
x≈0.785398+2kπ,k∈Z
Show Solution
