Trigonometry : Solving Equations using identities (Example 3) : ExamSolutions

Worked solution to a trig. equation using the identity sin squared x + cos squared x = 1 To see the revision guide goto ExamSolutions http://www.examsolutions.co.uk/

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• A-Level
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• Trigonometry
• equations
• identities
• examsolutions
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[brownchair94]

Hey, thanks very much for the all your video's, they've been a great help so far and i appreciate them, however is there any chance you could do another example where you explain how to solve an equation after its been square rooted? for example if you had tan^2 x = 4 where after square rooting you get a positive and negative 2 value so when inversing tan you would use x = tan^-1 (-2 or +2). As when I get to the graph i become very confused as to how to work out the other values for X (theta).

[ExamSolutions]

@brownchair94 I am sorry but I will not have time to do this for you. However, you have it slightly wrong. 2x = tan(-1) of 2 or -2. So 2x = 63.4 ... , 180 + 63.4, etc then divide each by 2. Do the same for 2x = tan(-1) of -2. Sorry to be brief but I have another ton of questions to answer from comments at the moment.

[rophiat]

for d d formular can u also make sin squared tita d subject formular instead of cos squared tita

[ExamSolutions]

@rophiat not really as there is only one term in squared not a sin squared

[221849466]

wait I don't get it, shouldn't the 2 be a -2 not a +2.

3-5=-2

[ExamSolutions]

@221849466 I sitched sides so it was 5-3

[snowmandashdash]

when you were finding the values for theta with sin(theta)=1, how would you do it using the quadrant method? because i did it that way and got 0,90 and 360...

[xxwhyamistillsingle]

at the 6th step can you just straight away use the calculator to find the answers for both thetas?

[brownchair94]

@ExamSolutions No Worries, thanks a bunch :)

[sharpshiell]

wait my bad i see my mistake

[sharpshiell]

agreed it should have been -2 not +2