ACT Math : How to find positive tangent

Study concepts, example questions & explanations for ACT Math

varsity tutors app store varsity tutors android store varsity tutors ibooks store

Example Questions

Example Question #1 : How To Find Positive Tangent

Math2

For triangle \displaystyle \DeltaABC\displaystyle \Delta ABC, what is the cotangent of angle \displaystyle \angle B?

Possible Answers:

\displaystyle \frac{d}{e}

\displaystyle \frac{d}{f}

\displaystyle \frac{f}{d}

\displaystyle \frac{f}{e}

Correct answer:

\displaystyle \frac{f}{d}

Explanation:

The cotangent of the angle of a triangle is the adjacent side over the opposite side. The answer is \displaystyle \frac{f}{d}

 

Math2-p1

Example Question #2 : How To Find Positive Tangent

What is the tangent of the angle formed between the origin and the point \displaystyle (-12,-5) if that angle is formed with one side of the angle beginning on the \displaystyle x-axis and then rotating counter-clockwise to \displaystyle (-12,-5)? Round to the nearest hundredth.

Possible Answers:

\displaystyle -0.42

\displaystyle -2.4

\displaystyle 0.38

\displaystyle 2.4

\displaystyle 0.42

Correct answer:

\displaystyle 0.42

Explanation:

Recall that when you calculate a trigonometric function for an obtuse angle like this, you always use the \displaystyle x-axis as your reference point for your angle. (Hence, it is called the "reference angle.")  

Now, it is easiest to think of this like you are drawing a little triangle in the third quadrant of the Cartesian plane. It would look like: 

Tan125

So, the tangent of an angle is:

\displaystyle \frac{opposite}{adjacent}  or, for your data, \displaystyle \frac{5}{12}

This is \displaystyle 0.41666666666667. Rounding, this is \displaystyle 0.42.  Since \displaystyle (-12,-5) is in the third quadrant, your value must be positive, as the tangent function is positive in that quadrant.

Example Question #23 : Trigonometry

What is the tangent of the angle formed between the origin and the point \displaystyle (-5,-16) if that angle is formed with one side of the angle beginning on the \displaystyle x-axis and then rotating counter-clockwise to \displaystyle (-5,-16)? Round to the nearest hundredth.

Possible Answers:

\displaystyle 5.14

\displaystyle -3.2

\displaystyle 3.2

\displaystyle 0.31

\displaystyle -0.31

Correct answer:

\displaystyle 3.2

Explanation:

Recall that when you calculate a trigonometric function for an obtuse angle like this, you always use the \displaystyle x-axis as your reference point for your angle. (Hence, it is called the "reference angle.")  

Now, it is easiest to think of this like you are drawing a little triangle in the third quadrant of the Cartesian plane. It would look like: 

Tan516

So, the tangent of an angle is:

\displaystyle \frac{opposite}{adjacent}  or, for your data, \displaystyle \frac{16}{5}, or \displaystyle 3.2. Since \displaystyle (-5,-16) is in the third quadrant, your value must be positive, as the tangent function is positive in this quadrant.

Example Question #1 : How To Find Positive Tangent

A ramp is being built at an angle of \displaystyle 30^{\circ} from the ground. It must cover \displaystyle 10 horizontal feet. What is the length of the ramp? Round to the nearest hundredth of a foot.

Possible Answers:

\displaystyle 13.53\:ft

\displaystyle 11.55\:ft

\displaystyle 16.91\:ft

\displaystyle 12.41\:ft

\displaystyle 5.77\:ft

Correct answer:

\displaystyle 11.55\:ft

Explanation:

Based on our information, we can draw this little triangle:


Tan10

Since we know that the tangent of an angle is \displaystyle \frac{opposite}{adjacent}, we can say:

\displaystyle tan(30)=\frac{y}{10}

This can be solved using your calculator:

\displaystyle y=10tan(30) or \displaystyle 5.77350269189626

Now, to solve for \displaystyle r, use the Pythagorean Theorem, \displaystyle a^2+b^2=c^2, where \displaystyle a and \displaystyle b are the legs of a triangle and \displaystyle c is the triangle's hypotenuse. Here, \displaystyle c=r, so we can substitute that in and rearrange the equation to solve for \displaystyle r:

\displaystyle r=\sqrt{a^2+b^2}

Substituting in the known values:

\displaystyle r=\sqrt{10^2+5.77350269189626^2}, or approximately \displaystyle 11.54700538379252. Rounding, this is \displaystyle 11.55.

Learning Tools by Varsity Tutors