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Popular >

sec^2(θ)-9=0

Solution

sec^{2} (θ) - 9 = 0

Solution

θ = 1.23095 \dots + 2 πn, θ = 2 π - 1.23095 \dots + 2 πn, θ = 1.91063 \dots + 2 πn, θ = - 1.91063 \dots + 2 πn

+1

Degrees

θ = 70.52877 \dots^{\circ} + 36 0^{\circ} n, θ = 289.47122 \dots^{\circ} + 36 0^{\circ} n, θ = 109.47122 \dots^{\circ} + 36 0^{\circ} n, θ = - 109.47122 \dots^{\circ} + 36 0^{\circ} n

Solution steps

sec^{2} (θ) - 9 = 0

Solve by substitution

sec^{2} (θ) - 9 = 0

Let:

sec (θ) = u

u^{2} - 9 = 0

u^{2} - 9 = 0 : u = 3, u = - 3

u^{2} - 9 = 0

Move

9

to the right side

u^{2} - 9 = 0

Add

9

to both sides

u^{2} - 9 + 9 = 0 + 9

Simplify

u^{2} = 9

u^{2} = 9

For

x^{2} = f (a)

the solutions are

x = f (a), - f (a)

u = 9, u = - 9

9 = 3

9

Factor the number:

9 = 3^{2}

= 3^{2}

Apply radical rule:

3^{2} = 3

= 3

- 9 = - 3

- 9

9 = 3

9

Factor the number:

9 = 3^{2}

= 3^{2}

Apply radical rule:

3^{2} = 3

= 3

= - 3

u = 3, u = - 3

Substitute back

u = sec (θ)

sec (θ) = 3, sec (θ) = - 3

sec (θ) = 3, sec (θ) = - 3

sec (θ) = 3 : θ = arcsec (3) + 2 πn, θ = 2 π - arcsec (3) + 2 πn

sec (θ) = 3

Apply trig inverse properties

sec (θ) = 3

General solutions for

sec (θ) = 3

sec (x) = a \Rightarrow x = arcsec (a) + 2 πn, x = 2 π - arcsec (a) + 2 πn

θ = arcsec (3) + 2 πn, θ = 2 π - arcsec (3) + 2 πn

θ = arcsec (3) + 2 πn, θ = 2 π - arcsec (3) + 2 πn

sec (θ) = - 3 : θ = arcsec (- 3) + 2 πn, θ = - arcsec (- 3) + 2 πn

sec (θ) = - 3

Apply trig inverse properties

sec (θ) = - 3

General solutions for

sec (θ) = - 3

sec (x) = - a \Rightarrow x = arcsec (- a) + 2 πn, x = - arcsec (- a) + 2 πn

θ = arcsec (- 3) + 2 πn, θ = - arcsec (- 3) + 2 πn

θ = arcsec (- 3) + 2 πn, θ = - arcsec (- 3) + 2 πn

Combine all the solutions

θ = arcsec (3) + 2 πn, θ = 2 π - arcsec (3) + 2 πn, θ = arcsec (- 3) + 2 πn, θ = - arcsec (- 3) + 2 πn

Show solutions in decimal form

θ = 1.23095 \dots + 2 πn, θ = 2 π - 1.23095 \dots + 2 πn, θ = 1.91063 \dots + 2 πn, θ = - 1.91063 \dots + 2 πn

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