Since π < x < 3 π 2 \pi < x < \frac{3\pi}{2} π < x < 2 3 π , x x x lies in the third quadrant. In the third quadrant, both sin x \sin x sin x and cos x \cos x cos x are negative, and tan x \tan x tan x is positive.
We have sin x = − 3 5 \sin x = -\frac{3}{5} sin x = − 5 3 . Using the identity sin 2 x + cos 2 x = 1 \sin^2 x + \cos^2 x = 1 sin 2 x + cos 2 x = 1 , we can find cos x \cos x cos x . cos 2 x = 1 − sin 2 x = 1 − ( − 3 5 ) 2 = 1 − 9 25 = 16 25 \cos^2 x = 1 - \sin^2 x = 1 - (-\frac{3}{5})^2 = 1 - \frac{9}{25} = \frac{16}{25} cos 2 x = 1 − sin 2 x = 1 − ( − 5 3 ) 2 = 1 − 25 9 = 25 16 Since cos x \cos x cos x is negative in the third quadrant, we have cos x = − 16 25 = − 4 5 \cos x = -\sqrt{\frac{16}{25}} = -\frac{4}{5} cos x = − 25 16 = − 5 4 .
Now, we can find tan x \tan x tan x : tan x = sin x cos x = − 3 5 − 4 5 = 3 4 \tan x = \frac{\sin x}{\cos x} = \frac{-\frac{3}{5}}{-\frac{4}{5}} = \frac{3}{4} tan x = c o s x s i n x = − 5 4 − 5 3 = 4 3
We also have csc x = 1 sin x = 1 − 3 5 = − 5 3 \csc x = \frac{1}{\sin x} = \frac{1}{-\frac{3}{5}} = -\frac{5}{3} csc x = s i n x 1 = − 5 3 1 = − 3 5 .
We want to find the value of 80 ( tan 2 x − csc x ) 80(\tan^2 x - \csc x) 80 ( tan 2 x − csc x ) . Substituting the values we found:
80 ( tan 2 x − csc x ) = 80 ( ( 3 4 ) 2 − ( − 5 3 ) ) = 80 ( 9 16 + 5 3 ) = 80 ( 27 + 80 48 ) = 80 ( 107 48 ) = 80 48 × 107 = 5 3 × 107 = 535 3 = 178.33 80(\tan^2 x - \csc x) = 80((\frac{3}{4})^2 - (-\frac{5}{3})) = 80(\frac{9}{16} + \frac{5}{3}) = 80(\frac{27 + 80}{48}) = 80(\frac{107}{48}) = \frac{80}{48} \times 107 = \frac{5}{3} \times 107 = \frac{535}{3} = 178.33 80 ( tan 2 x − csc x ) = 80 (( 4 3 ) 2 − ( − 3 5 )) = 80 ( 16 9 + 3 5 ) = 80 ( 48 27 + 80 ) = 80 ( 48 107 ) = 48 80 × 107 = 3 5 × 107 = 3 535 = 178.33 However, this is not one of the options. Let us check the expression again.
We are given the expression 80 ( tan 2 x − csc x ) 80(\tan^2 x - \csc x) 80 ( tan 2 x − csc x ) .
We found that sin x = − 3 5 \sin x = -\frac{3}{5} sin x = − 5 3 , cos x = − 4 5 \cos x = -\frac{4}{5} cos x = − 5 4 , tan x = 3 4 \tan x = \frac{3}{4} tan x = 4 3 , and csc x = − 5 3 \csc x = -\frac{5}{3} csc x = − 3 5 .
Now let us calculate 80 ( tan 2 x − csc x ) 80(\tan^2 x - \csc x) 80 ( tan 2 x − csc x ) . 80 ( tan 2 x − csc x ) = 80 ( ( 3 4 ) 2 − ( − 5 3 ) ) = 80 ( 9 16 + 5 3 ) = 80 ( 27 + 80 48 ) = 80 ( 107 48 ) = 5 3 ( 107 ) = 535 3 ≈ 178.33 80(\tan^2 x - \csc x) = 80((\frac{3}{4})^2 - (-\frac{5}{3})) = 80(\frac{9}{16} + \frac{5}{3}) = 80(\frac{27+80}{48}) = 80(\frac{107}{48}) = \frac{5}{3}(107) = \frac{535}{3} \approx 178.33 80 ( tan 2 x − csc x ) = 80 (( 4 3 ) 2 − ( − 3 5 )) = 80 ( 16 9 + 3 5 ) = 80 ( 48 27 + 80 ) = 80 ( 48 107 ) = 3 5 ( 107 ) = 3 535 ≈ 178.33
Let's re-examine the expression and the provided options. It is possible there's a typo. Perhaps the expression should be 80 ( tan x − csc 2 x ) 80(\tan x - \csc^2 x) 80 ( tan x − csc 2 x ) or something else. Let us assume the question is 80 ( tan x − csc x ) = 80 ( 3 4 − ( − 5 3 ) ) = 80 ( 9 + 20 12 ) = 80 ( 29 12 ) = 20 ⋅ 29 3 = 580 3 80(\tan x - \csc x) = 80(\frac{3}{4} - (-\frac{5}{3})) = 80(\frac{9+20}{12}) = 80(\frac{29}{12}) = \frac{20 \cdot 29}{3} = \frac{580}{3} 80 ( tan x − csc x ) = 80 ( 4 3 − ( − 3 5 )) = 80 ( 12 9 + 20 ) = 80 ( 12 29 ) = 3 20 ⋅ 29 = 3 580 which is not an integer either.
The original expression is 80 ( tan 2 x − csc x ) 80(\tan^2 x - \csc x) 80 ( tan 2 x − csc x ) . We calculated tan x = 3 4 \tan x = \frac{3}{4} tan x = 4 3 , csc x = − 5 3 \csc x = -\frac{5}{3} csc x = − 3 5 . So 80 ( tan 2 x − csc x ) = 80 ( 9 16 + 5 3 ) = 80 ( 27 + 80 48 ) = 5 3 ( 107 ) = 535 3 ≈ 178.33 80(\tan^2 x - \csc x) = 80(\frac{9}{16} + \frac{5}{3}) = 80(\frac{27+80}{48}) = \frac{5}{3}(107) = \frac{535}{3} \approx 178.33 80 ( tan 2 x − csc x ) = 80 ( 16 9 + 3 5 ) = 80 ( 48 27 + 80 ) = 3 5 ( 107 ) = 3 535 ≈ 178.33 . There seems to be an error in the problem statement, as the result is not an integer, and none of the options are close. Let us try evaluating 80 ( tan 2 ( x ) ) − 80 csc ( x ) = 80 ( 9 16 ) − 80 ( − 5 3 ) = 45 + 400 3 = 135 + 400 3 = 535 3 ≈ 178.33 80(\tan^2(x)) - 80\csc(x) = 80(\frac{9}{16}) - 80(-\frac{5}{3}) = 45 + \frac{400}{3} = \frac{135+400}{3} = \frac{535}{3} \approx 178.33 80 ( tan 2 ( x )) − 80 csc ( x ) = 80 ( 16 9 ) − 80 ( − 3 5 ) = 45 + 3 400 = 3 135 + 400 = 3 535 ≈ 178.33 It is likely there is a typo and it is meant to be csc 2 x \csc^2 x csc 2 x 80 ( tan 2 x + csc 2 x ) = 80 ( 9 16 + 25 9 ) = 80 ( 81 + 400 144 ) = 80 481 144 = 10 ∗ 481 18 = 5 ∗ 481 9 ≈ 267 80(\tan^2 x + \csc^2 x) = 80 (\frac{9}{16} + \frac{25}{9}) = 80(\frac{81+400}{144}) = 80 \frac{481}{144} = \frac{10*481}{18} = \frac{5*481}{9} \approx 267 80 ( tan 2 x + csc 2 x ) = 80 ( 16 9 + 9 25 ) = 80 ( 144 81 + 400 ) = 80 144 481 = 18 10 ∗ 481 = 9 5 ∗ 481 ≈ 267
There is a typo in the problem, let us assume it should be 80 ( cot 2 ( x ) − csc ( x ) ) = 80 ( 16 9 + 5 3 ) = 80 16 + 15 9 = 80 ∗ 31 9 ≈ 275 80(\cot^2(x) - \csc(x))= 80(\frac{16}{9} + \frac{5}{3}) = 80\frac{16 + 15}{9} = 80*\frac{31}{9} \approx 275 80 ( cot 2 ( x ) − csc ( x )) = 80 ( 9 16 + 3 5 ) = 80 9 16 + 15 = 80 ∗ 9 31 ≈ 275 .
If the expression was 80 ( cot x − csc x ) 80(\cot x - \csc x) 80 ( cot x − csc x ) Then c o t x = 4 3 S o 80 ( 4 3 + 5 3 = 80 ∗ 3 = 240 cot x = \frac{4}{3} So 80(\frac{4}{3} + \frac{5}{3} = 80 * 3 = 240 co t x = 3 4 S o 80 ( 3 4 + 3 5 = 80 ∗ 3 = 240
It seems the problem has errors. The options are also integers.
If instead of 80, it said 18,
If it were 18 ( t a n 2 ( x ) − c s c ( x ) ) 18(tan^2(x) - csc(x)) 18 ( t a n 2 ( x ) − csc ( x )) , we get 18 ( 9 16 − ( − 5 3 ) ) = 18 9 16 + 18 5 3 = 18 ∗ ( 27 + 80 48 = 54 + 180 3 = 1206 48 = 18 ( 107 48 = 9 ( 107 ) 24 ≈ 321 8 = 37.5 18 (\frac{9}{16} - (-\frac{5}{3})) = 18 \frac{9}{16} + 18 \frac{5}{3} = 18*(\frac{27+80}{48} = \frac{54 + 180}{3} = \frac{1206}{48} = 18 (\frac{107}{48} = \frac{9(107)}{24} \approx \frac{321}{8} =37.5 18 ( 16 9 − ( − 3 5 )) = 18 16 9 + 18 3 5 = 18 ∗ ( 48 27 + 80 = 3 54 + 180 = 48 1206 = 18 ( 48 107 = 24 9 ( 107 ) ≈ 8 321 = 37.5
Given the problem and answer choices, there are errors either in the question or the provided answer choices.