Respuesta :

MathPhys

Answer:

cos θ = -5/13

Step-by-step explanation:

sin θ = -12/13

Use Pythagorean identity.

sin²θ + cos²θ = 1

(-12/13)² + cos²θ = 1

144/169 + cos²θ = 1

cos²θ = 25/169

cos θ = ±5/13

θ is in the 3rd quadrant, so cos θ < 0.

cos θ = -5/13

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