Can you solve 9sin^2theta - 6sintheta = 1 over [0 degree, 360 degrees) ?

Answer 1

#theta=53.58 color(white)(888)# and #color(white)(888)theta=126.42#

#theta=352.06 color(white)(888)# and # color(white)(888)theta=187.93 color(white)(888)# ( 2 d.p. )

#9sin^2(theta)-6sin(theta)=1#
#9sin^2(theta)-6sin(theta)-1=0#

This is just a quadratic equation, which we can easily solve:

Let # \ \ \ \u=sin(theta)#

Then:

#9u^2-6u-1=0#

Using quadratic formula:

#u=(-b+-sqrt(b^2-4ac))/(2a)#
#u=(-(-6)+-sqrt((-6)^2-(4(9)(-1))))/((2)(9))#
#u=(6+-sqrt(72))/(18)#
#u=(1+-sqrt(2))/3#
But # \ \ \ \ u=sin(theta)#
#sin(theta)=(1+sqrt(2))/3#
#sin(theta)=(1-sqrt(2))/3#
#theta=arcsin(sin(theta))=arcsin((1+sqrt(2))/3)#
#theta=arcsin(sin(theta))=arcsin((1-sqrt(2))/3)#

For:

#[0,360]#
#theta=arcsin((1+sqrt(2))/3)# and #theta=180-arcsin((1+sqrt(2))/3)#
#theta=360+arcsin((1-sqrt(2))/3)#

and

#theta=180-arcsin((1-sqrt(2))/3)#

Approximate values:

#theta=53.58 color(white)(888)# and #color(white)(888)theta=126.42#
#theta=352.06 color(white)(888)# and # color(white)(888)theta=187.93 color(white)(888)# ( 2 d.p. )
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Answer 2

To solve the equation 9sin2(θ)6sin(θ)=19\sin^2(\theta) - 6\sin(\theta) = 1 over the interval [0,360)[0^\circ, 360^\circ), we can first rewrite it as a quadratic equation in terms of sin(θ)\sin(\theta):

9sin2(θ)6sin(θ)1=09\sin^2(\theta) - 6\sin(\theta) - 1 = 0

Now, let u=sin(θ)u = \sin(\theta), then the equation becomes:

9u26u1=09u^2 - 6u - 1 = 0

This is a quadratic equation, which we can solve using the quadratic formula:

u=b±b24ac2au = \frac{{-b \pm \sqrt{{b^2 - 4ac}}}}{{2a}}

where a=9a = 9, b=6b = -6, and c=1c = -1.

Plugging in the values:

u=(6)±(6)24(9)(1)2(9)u = \frac{{-(-6) \pm \sqrt{{(-6)^2 - 4(9)(-1)}}}}{{2(9)}}

u=6±36+3618u = \frac{{6 \pm \sqrt{{36 + 36}}}}{{18}}

u=6±7218u = \frac{{6 \pm \sqrt{72}}}{{18}}

u=6±6218u = \frac{{6 \pm 6\sqrt{2}}}{{18}}

u=1±23u = \frac{{1 \pm \sqrt{2}}}{{3}}

Now, we have two possible solutions for uu:

  1. u=1+23u = \frac{{1 + \sqrt{2}}}{{3}}
  2. u=123u = \frac{{1 - \sqrt{2}}}{{3}}

Since sin(θ)=u\sin(\theta) = u, we need to find the corresponding values of θ\theta within the given interval [0,360)[0^\circ, 360^\circ).

For u=1+23u = \frac{{1 + \sqrt{2}}}{{3}}: θ=sin1(1+23)\theta = \sin^{-1}\left(\frac{{1 + \sqrt{2}}}{{3}}\right)

For u=123u = \frac{{1 - \sqrt{2}}}{{3}}: θ=sin1(123)\theta = \sin^{-1}\left(\frac{{1 - \sqrt{2}}}{{3}}\right)

Once we have obtained the values of θ\theta, we need to ensure they fall within the interval [0,360)[0^\circ, 360^\circ).

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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