Find the Other Trig Values in Quadrant III cos(0)=-4/5

$\cos (0) = - \frac{4}{5}$

Step 1

Use the definition of cosine to find the known sides of the unit circle right triangle. The quadrant determines the sign on each of the values.

$\cos (0) = \frac{adjacent}{hypotenuse}$

Step 2

Find the opposite side of the unit circle triangle. Since the adjacent side and hypotenuse are known, use the Pythagorean theorem to find the remaining side.

$Opposite = - \sqrt{{hypotenuse}^{2} - {adjacent}^{2}}$

Step 3

Replace the known values in the equation.

$Opposite = - \sqrt{{(5)}^{2} - {(- 4)}^{2}}$

Step 4

Simplify inside the radical.

Negate $\sqrt{{(5)}^{2} - {(- 4)}^{2}}$ .

Opposite $= - \sqrt{{(5)}^{2} - {(- 4)}^{2}}$

Raise $5$ to the power of $2$ .

Opposite $= - \sqrt{25 - {(- 4)}^{2}}$

Raise $- 4$ to the power of $2$ .

Opposite $= - \sqrt{25 - 1 \cdot 16}$

Multiply $- 1$ by $16$ .

Opposite $= - \sqrt{25 - 16}$

Subtract $16$ from $25$ .

Opposite $= - \sqrt{9}$

Rewrite $9$ as $3^{2}$ .

Opposite $= - \sqrt{3^{2}}$

Pull terms out from under the radical, assuming positive real numbers.

Opposite $= - 1 \cdot 3$

Multiply $- 1$ by $3$ .

Opposite $= - 3$

Step 5

Find the value of sine.

Use the definition of sine to find the value of $\sin (0)$ .

$\sin (0) = \frac{opp}{hyp}$

Substitute in the known values.

$\sin (0) = \frac{- 3}{5}$

Move the negative in front of the fraction.

$\sin (0) = - \frac{3}{5}$

Step 6

Find the value of tangent.

Use the definition of tangent to find the value of $\tan (0)$ .

$\tan (0) = \frac{opp}{adj}$

Substitute in the known values.

$\tan (0) = \frac{- 3}{- 4}$

Dividing two negative values results in a positive value.

$\tan (0) = \frac{3}{4}$

Step 7

Find the value of cotangent.

Use the definition of cotangent to find the value of $\cot (0)$ .

$\cot (0) = \frac{adj}{opp}$

Substitute in the known values.

$\cot (0) = \frac{- 4}{- 3}$

Dividing two negative values results in a positive value.

$\cot (0) = \frac{4}{3}$

Step 8

Find the value of secant.

Use the definition of secant to find the value of $\sec (0)$ .

$\sec (0) = \frac{hyp}{adj}$

Substitute in the known values.

$\sec (0) = \frac{5}{- 4}$

Move the negative in front of the fraction.

$\sec (0) = - \frac{5}{4}$

Step 9

Find the value of cosecant.

Use the definition of cosecant to find the value of $\csc (0)$ .

$\csc (0) = \frac{hyp}{opp}$

Substitute in the known values.

$\csc (0) = \frac{5}{- 3}$

Move the negative in front of the fraction.

$\csc (0) = - \frac{5}{3}$

Step 10

This is the solution to each trig value.

$\sin (0) = - \frac{3}{5}$

$\cos (0) = - \frac{4}{5}$

$\tan (0) = \frac{3}{4}$

$\cot (0) = \frac{4}{3}$

$\sec (0) = - \frac{5}{4}$

$\csc (0) = - \frac{5}{3}$

Find the Other Trig Values in Quadrant III cos(0)=-4/5

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