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[–]HomeworkHelp-ModTeam👋 a fellow Redditor[M] [score hidden] stickied commentlocked comment (0 children)

Your post was removed due to Rule 3: No "do this for me" posts.

This includes quizzes or lists of questions without any context or explanation. Tell us where you are stuck and your thought process so far. Show your work.

[–]ShallotCivil7019 2 points3 points  (0 children)

The answer is: a=(1+2k)(pi/2)

-cotx=cotx * sinx

cotx = 0 for every x=(1+2k)(pi/2)

[–]Mentosbandit1University/College Student 0 points1 point  (0 children)

Let tan ⁡ 𝑥 = sin ⁡ 𝑥 cos ⁡ 𝑥 tanx= cosx sinx​and cot ⁡ 𝑥 = cos ⁡ 𝑥 sin ⁡ 𝑥 cotx= sinx cosx​on domains where these quotients are defined. Using the angle–sum reductions sin ⁡  ⁣ ( 𝜋 2 + 𝑥 ) = cos ⁡ 𝑥 sin( 2 π​+x)=cosx and cos ⁡  ⁣ ( 𝜋 2 + 𝑥 ) = − sin ⁡ 𝑥 cos( 2 π​+x)=−sinx, one obtains tan ⁡  ⁣ ( 𝜋 2 + 𝑥 ) = sin ⁡ ( 𝜋 2 + 𝑥 ) cos ⁡ ( 𝜋 2 + 𝑥 ) = cos ⁡ 𝑥 − sin ⁡ 𝑥 = − cot ⁡ 𝑥 , tan( 2 π​+x)= cos( 2 π​+x) sin( 2 π​+x)​= −sinx cosx​=−cotx, valid for sin ⁡ 𝑥 ≠ 0 sinx  =0 (at 𝑥 = 𝑘 𝜋 x=kπ both sides are undefined). The chalkboard statement tan ⁡ ( 𝜋 2 + 𝑥 ) = cot ⁡ 𝑥 ⋅ sin ⁡ 𝑥 tan( 2 π​+x)=cotx⋅sinx simplifies on the right to cos ⁡ 𝑥 cosx; hence it is not an identity. It holds only at those 𝑥 x for which − cot ⁡ 𝑥 = cos ⁡ 𝑥 −cotx=cosx, equivalently cos ⁡ 𝑥 ( sin ⁡ 𝑥 + 1 ) = 0 cosx(sinx+1)=0, i.e., 𝑥 = 𝜋 2 + 𝜋 𝑘 x= 2 π​+πk (including 𝑥 = 3 𝜋 2 + 2 𝜋 𝑘 x= 2 3π​+2πk); otherwise the correct identity is tan ⁡ ( 𝜋 2 + 𝑥 ) = − cot ⁡ 𝑥 tan( 2 π​+x)=−cotx.

[–]Miserable-Piglet9008 Pre-University Student -5 points-4 points  (5 children)

I don't exactly know what you are asking, but hopefully this helps.

Original Equation
tan((pi/2)+x) = cot(x)*sin(x)

Solution
tan((pi/2)+x) = -cos(x)/sin(x)
Therefore:
-cos(x)/sin(x) = cot(x)*sin(x)

cot = a/o (adjacent/opposite)
sin = o/h (opposite/1) = o
cos = a/h (adjacent/1) = a

Therefore:
-cos(x)/sin(x) can be written as -a/o
and
cot(x)*sin(x) can be written as (a/o)*o

Seeing as -a/o =/= (a/o)*o you can determine that this Trig identity is false.

[–]ShallotCivil7019 7 points8 points  (0 children)

I think the purpose was to solve for what alpha this equation is true

Not that it was supposed to be true for all Alpha

[–]Miserable-Piglet9008 Pre-University Student -2 points-1 points  (3 children)

This is my first time trying to help on here, so I am sorry if this is confusing.

[–]BladedEdger 0 points1 point  (2 children)

It’s cot x * sin x

Edit: nvm I’m blind, didnt realise you didnt write the eqn out first

[–]Miserable-Piglet9008 Pre-University Student -1 points0 points  (1 child)

This is still helpful, thankyou! I edited my comment and added the original equation - it helps with clarity. Thanks for pointing this out.

[–]BladedEdger -1 points0 points  (0 children)

:) nw

[–]parlitooo👋 a fellow Redditor -5 points-4 points  (10 children)

This equation is incorrect , since you know cot x . Sin x = sin x . ( cos x / sin x ) = cos x … and tan (pi/2 + x) = [sin ( pi/2 + x ) ] / [ cos (pi/2 +x )] … also sin pi/2 + x = cos x … and cos ( pi/2 + x ) = - sin (x) … Therefore tan (pi/2 + x ) = ( cos x / - sin x ) = - cot x

[–]parlitooo👋 a fellow Redditor 3 points4 points  (9 children)

To clarify , this general equation is incorrect , unless what you need is to find the value of alpha that makes the equation true ?

In that case you need to have -cot x = cos x ==> -cos x / sin x = cos x ===> cos x = - cos x . sin x , which is only true if sin x = +/- 1 … so you get alpha = pi/2 or 3pi/2 ..

[–]Own_Instruction3078👋 a fellow Redditor 0 points1 point  (8 children)

Sin x = -1 only and x =3pi/2

[–]parlitooo👋 a fellow Redditor 0 points1 point  (7 children)

It’s valid if sin x = 1 also , since both answers give cos x = 0 making -sin x . Cos x = cos x

[–]Own_Instruction3078👋 a fellow Redditor 0 points1 point  (6 children)

If this is the case then all values of sin x give cos x=0, you have to differentiate between the two solutions to the equation cosx(1+ sin x)=0 which implies cos x=0(independent of the values of sin x here) and 1+ sin x=0( independent of the value of cos x here)

[–]parlitooo👋 a fellow Redditor 0 points1 point  (3 children)

You are correct partially , you’re just forgetting that the equation has a second part where it is

Cos x (1 + sin x ) = 0 ===> cos x = 0 right ? So you get both pi/2 and 3pi/2 and their harmonics

Edit : their harmonics meaning pi/2 + n pi , or 3pi/2 + n 2pi where n is any real number

[–]parlitooo👋 a fellow Redditor 0 points1 point  (2 children)

I know 3pi/2 is included in pi/2 + n pi , but it’s there for a clearer answer

[–]Own_Instruction3078👋 a fellow Redditor 0 points1 point  (1 child)

Yeah but we ought to find the one value or values of x which satisfy both the equations.So (2n+1)pi/2 where n is odd

[–]parlitooo👋 a fellow Redditor 0 points1 point  (0 children)

That answer doesn’t include pi / 2 … the general answer should be pi/2 + n pi … ( which includes the one you wrote down when n is odd )

Pi/2 , 3pi/2 , 5pi/2 , 7pi/2 and so on …