Question

Type the correct answer in each box. Use numerals instead of words. If necessary, use / for the fraction bar(s). Complete the statements below, simplify all ratios and keep them as improper fractions. If cos(θ) = and sin(θ) is negative, then sin(θ) = and tan(θ) = .

Answer 1

Question:

If cos(θ) =-8/17 and sin(θ) is negative, then sin(θ) = ___  and tan(θ) =___.

Answer:

$Sin\theta = \frac{-15}{17}$

$Tan\theta = \frac{15}{8}$

Step-by-step explanation:

Given

cos(θ) =-8/17

Required

sin(θ) = __

tan(θ) =__

The first step is to determine the length of the third side

Given that

$cos(\theta) = \frac{Adj}{Hyp}$

Where Adj and Hyp represent Adjacent and Hypotenuse

$cos(\theta) = \frac{-8}{17}$

By comparison

$Adj = -8\ and\ Hyp = 17$

Using Pythagoras

$Hyp^2 = Adj^2 + Opp^2$

By Substitution

$17^2 = (-8)^2 + Opp^2$

$289 = 64 + Opp^2$

Subtract 64 from both sides

$289 - 64 = 64 - 64 + Opp^2$

$225 = Opp^2$

Take square roots of both sides

$\sqrt{225} = \sqrt{Opp^2}$

$\sqrt{225} = Opp$

$15 = Opp$

$Opp = 15$

The question says that sin(θ) is negative; This implies that θ is in the third quadrant and as such

$Opp = -15$

From trigonometry

$Sin\theta = \frac{Opp}{Hyp}$

$Sin\theta = \frac{-15}{17}$

Also from trigonometry

$Tan\theta = Sin\theta / Cos\theta$

$Tan\theta = \frac{-15}{17} / \frac{-8}{17}$

$Tan\theta = \frac{-15}{17} * \frac{-17}{8}$

$Tan\theta = \frac{-15 * -17}{17 * 8}$

$Tan\theta = \frac{15 * 17}{17 * 8}$

$Tan\theta = \frac{15}{8}$