Question

The terminal side contains the point (-5, 12). Find sin θ.

Question 4 options:

-.923


-.385


.923


.385

Answer 1

sin theta = .923

Explanation:

see image. An angle in standard position has one side glued to the x-axis, and the other side-the terminal side- rotating around the origin. When it gets to (-5, 12) in your problem, it stops there. 5, 12are the legs of a right triangle and they are recognizable as part of a pythagorean triple 5,12,13. So the hypotenuse is 13. Sin is OPP/HYP. So that is 12/13. Its in the 2nd quadrant, so it should be positive. We used the reference angle, bc the actual angle is the >90° angle from the positive x-axis to thru (-5,12). It calcs the same tho.

sin theta = 12/13

= 0.923

Answer 2

(c) 0.923

Explanation:

The coordinates of a point on the unit circle are (cos(θ), sin(θ)). That is, the y-coordinate of a point on the terminal ray will have the same sign as the sine of the angle. Here, the sign of the sine is positive, eliminating the first two answer choices.

We know that cos(θ) < sin(θ) for reference angles greater than 45°, where both values are √2/2 ≈ 0.707. Since 5 < 12, that means the angle of interest here will have a sine that is more than 0.707. Only one of the positive answer choices is in this range: sin(θ) ≈ 0.923.

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Additional comment

The value of sin(θ) is precisely ...

sin(θ) = y/√(x²+y²) = 12/√(25+144) = 12/13

sin(θ) = 0.923076...(6-digit repeat)