Solve the equation

tan²3Θ = cot²a

this can't be sovled there are two variables and one equation

assuming a typo and you meant

tan^2 3a = cot^2 a

good luck. wolframalpha solves it, and you get

a = 2πn ± 2 arctan(1 ± √2)
and
a = 2πn ± 2 arctan(1 - √2 - √(4-2√2))

Making the same assumption as Steve,

recall that tan 45° and cot 45° = 1
as a matter of fact , both the tangent and cotangent of any ODD multiple of 45 is either +1 or -1
since both sides of the equation are squared, any multiple of 45° or π/4 radians will be a solution

e.g. let a = 495° (45x11)
LS = tan^2 (1485) = 1
RS = tan^2 (495) = (-1)^2 = 1

If we take even multiples of 45° we run into undefined situations in either the tangent or the cotangent
if the multiple is even and divisible by 4, then the
tangent is zero, but the cotangent would be undefined.
if the multiple is even and not divisible by 4, then the tangent is undefined, (cotangent would be zero)

Using the webpage that Steve suggested
http://www.wolframalpha.com/input/?i=%28tan%283x%29%29%5E2-1%2F%28tan%28x%29%29%5E2%3D0

shows that 22.5° or π/8 radians is also a solution.
A similar analysis of multiple of 22.5 can also be made

To solve the equation tan²(3Θ) = cot²a, we need to find the values of Θ and a that satisfy the equation. But before we dive into the solution, let's understand the trigonometric identities involved.

1. The tangent squared identity: tan²θ = sec²θ - 1
2. The cotangent squared identity: cot²θ = 1 - csc²θ

Now, let's proceed with solving the equation.

Step 1: Rewrite the equation using the identities above.
sec²(3Θ) - 1 = 1 - csc²a

Step 2: Simplify the equation by rearranging the terms.
sec²(3Θ) + csc²a = 2

Step 3: Since sec²θ = 1/cos²θ and csc²θ = 1/sin²θ, substitute these values in the equation.
1/(cos²(3Θ)) + 1/(sin²a) = 2

Step 4: Combine the fractions on the left-hand side by finding the common denominator, which is cos²(3Θ) * sin²a.
(sin²a + cos²(3Θ)) / (cos²(3Θ) * sin²a) = 2

Step 5: Notice that sin²a + cos²θ = 1 (the Pythagorean identity).
1 / (cos²(3Θ) * sin²a) = 2

Step 6: Multiply both sides of the equation by cos²(3Θ) * sin²a.
1 = 2 * cos²(3Θ) * sin²a

Step 7: Divide both sides of the equation by 2.
1/2 = cos²(3Θ) * sin²a

Step 8: Recall that sin²θ = 1 - cos²θ (the Pythagorean identity) and substitute this value in the equation.
1/2 = cos²(3Θ) * (1 - cos²a)

Step 9: Distribute cos²(3Θ) across the parentheses.
1/2 = cos²(3Θ) - cos²(3Θ) * cos²a

Step 10: Rearrange the terms.
cos²(3Θ) * cos²a - cos²(3Θ) = 1/2

Step 11: Factor out cos²(3Θ).
cos²(3Θ) * (cos²a - 1) = 1/2

Step 12: Divide both sides of the equation by (cos²a - 1).
cos²(3Θ) = (1/2) / (cos²a - 1)

Step 13: Take the square root of both sides.
cos(3Θ) = ±√((1/2) / (cos²a - 1))

Step 14: Solve for 3Θ by taking the inverse cosine of both sides.
3Θ = ±acos(√((1/2) / (cos²a - 1)))

Step 15: Solve for Θ by dividing both sides by 3.
Θ = ±(1/3)acos(√((1/2) / (cos²a - 1)))

Therefore, the solutions for the equation tan²(3Θ) = cot²a are given by the values of Θ obtained from the equation above.