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emilyliv emilyliv
wrote...
Posts: 154
Rep: 3 0
3 years ago
c) tan (90° - 2θ) = 1.6443
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wrote...
Educator
3 years ago
Maybe this will help?



To the nearest degree, that is 16.
emilyliv Author
wrote...
3 years ago
yes but there's more than one answer, 16 degrees is one of them but there is also 106, 196, and 286
wrote...
Educator
3 years ago Edited: 3 years ago, bio_man
Here are my thoughts:

If the ratio is positive +1.6443, that means there are 2 angles that give this ratio, one that's in the 1st quadrant and one in the 3rd (remember the CAST rule).

Now, we found theta to be 16°, so substituting that into 90 - 2θ:

90 - 2(16) = 58°

58° is an acute angle, so we can use this to find the other hidden angle in quadrant 3:

180 + 58 = 238°



Using 90 - 2θ, we can solve for yet another theta:

90 - 2θ = 238
238-90 = -2θ
θ = -74

** Unfortunately, we can't use negative angles because of the restrictions given in the question, so we can get its coterminal angles by adding 360 to it, giving use 286°.



Using the coterminal approach, subtracting 58 minus 360 gives use another hidden angle, -302°.

Using 90 - 2θ, we can solve for yet another theta:

90 - 2θ = -302
-302-90 = -2θ
θ = 196°



Using the coterminal approach for 238°, subtracting 238° minus 360 gives use another hidden angle, -122°.

Using 90 - 2θ, we can solve for yet another theta:

90 - 2θ = -122
-122-90 = -2θ
θ = 106°

Such an annoying question -- let me know if you need further help
emilyliv Author
wrote...
3 years ago
Everything makes sense, except I was confused on why you had to use 58 to subtract from 360, as well as 238.
wrote...
Educator
3 years ago
When you add 360 or subtract 360 from any angle, you get a new angle that will have the same ratio. After finding that tan(58) = 1.6443 and tan(238) = 1.6443, I figured that if I add 360 to 58, I will get 418, and when solving for theta in the expression, it will give me a value between 0 and 360.

An explanation here:

emilyliv Author
wrote...
3 years ago
okay, that makes sense, thank you again!
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