Stuck on supposedly easy C3 Trig Q?

Its from Edexcel C3 Exercise 2.2 Part 1d

I understand how to get the first angle, but do you get the rest?

ANS: 31.7, -58.3, 121.7, -148.3

Original post by NickyConfused

Its from Edexcel C3 Exercise 2.2 Part 1d

I understand how to get the first angle, but do you get the rest?

ANS: 31.7, -58.3, 121.7, -148.3

I think it's easier just to get a principle value for 2x, find x and consider all subsequent solutions +/90n degrees on.

Original post by NickyConfused

...

Everything fine up to

\tan t = 2

.

While

t = \tan^{-1} 2 = 121.7^{\circ}

is true, remember that

\tan t = \tan (t \pm 180^{\circ})

so there are other solutions.

Another hint is

-180^{\circ} \leq x \leq 180^{\circ} \Rightarrow -360^{\circ} \leq t \leq 360^{\circ}

.

Good luck. :smile:

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