All ACT Math Resources
Example Questions
Example Question #31 : Cosine
What is cos θ?
cos = adjacent/hypotenuse =
To get the radical out of the denominator, we multiply:
Example Question #3 : How To Find The Cosine Of An Angle
What is the cosine of the angle formed between the -axis and the line passing through with a slope of ? Round to the nearest hundredth.
You do not even need to compute the line for this question. All that you need to do is note that you can make a little right triangle with a height of and a base of , which you get from the slope of the line. So, to compute the cosine, you will need to find the hypotenuse using the Pythagorean theorem:
So, our little triangle looks like:
The cosine will be the adjacent side, , divided by the hypotenuse, :
, or approximately .
Example Question #125 : Trigonometry
What is the of an angle with ?
Since the sine of the angle is , that means the opposite side of the triangle is and the hypotenuse is . Automatically, you know this is a special 3-4-5 right triangle, and that the missing side is 3. If not, you could also find the 3rd side by doing Pythagorean Theorem. This gives you your answer of
Example Question #3041 : Act Math
Right triangle has sides , and . What is the cosine of ?
SOHCAHTOA tells us that , and we know the hypotenuse is the longest side of the triangle, . Our adjacent side will be the other side that has as a vertex, .
Thus, .
Example Question #3041 : Act Math
Right triangle has sides , and . What is the cosine of ?
SOHCAHTOA tells us that , and we know the hypotenuse is the longest side of the triangle, . Our adjacent side will be the other side that has as a vertex, .
Thus, .
Example Question #1 : How To Find Positive Cosine
The value of a cosine is positive in which quadrants?
The 1st and 4th
The 3rd only
The 1st and 3rd
The 4th only
The 1st and 4th
The cosine is positive in the 1st and 4th quadrants and negative in 2nd and 3rd
Example Question #32 : Cosine
Which of the following is equal to ?
Here, we use the SOHCAHTOA ratios and the fact that csc x = 1 / sin x.
Cosine x = adjacent side length / hypotenuse length
Cosecant x = 1 / sin x = hypotenuse / opposite
(Adjacent / hypotenuse) * (hypotenuse / opposite) = Adjacent / opposite = Cotangent x.
Example Question #2 : How To Find Positive Cosine
and is between and . What is the value of ?
For to , we know that . So, the question asks, what is the value of , where . Therefore, it is asking what the value of is, which is .
Example Question #2 : How To Find Positive Cosine
To the nearest , what is the cosine formed from the origin to ? Assume counterclockwise rotation.
If the point to be reached is , then we may envision a right triangle with sides and , and hypotenuse . The Pythagorean Theorem tells us that , so we plug in and find that:
Thus,
Now, SOHCAHTOA tells us that , so we know that:
Thus, our cosine is approximately .
Example Question #131 : Trigonometry
Two drivers race to a finish line. Driver A drives north blocks, and east blocks and crosses the goal. Driver B drives the shortest direct route between the two points. Relative to east, what is the cosine of the angle at which Driver B raced? Round to the nearest .
If the point to be reached is blocks north and blocks east, then we may envision a right triangle with sides and , and hypotenuse . The Pythagorean Theorem tells us that , so we plug in and find that:
Thus,
Now, SOHCAHTOA tells us that , so we know that:
Thus, our cosine is approximately .
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