All ACT Math Resources
Example Questions
Example Question #2 : How To Find The Sine Of An Angle
If , , and , what is the sine of ?
Recall that sin = opposite / hypotenuse. Based on the figure shown, we see that is the opposite side needed and is the hypotenuse. Plug these values in to solve.
Example Question #3 : How To Find The Sine Of An Angle
Triangle shown is a right triangle. If line and line , what is the sine of the angle at ?
Now solve for using Pythagorean Theorem:
Example Question #3 : How To Find The Sine Of An Angle
If , and if is an angle between and degrees, which of the following equals ?
An angle between and degrees means that the angle is located in the second quadrant.
The tangent function is derived from taking the side opposite to the angle and dividing by the side adjacent to the angle (, as shown in the image).
Hence, the side is units long and side is units high. Therefore, according to Pythagorean Theorem rules, the side must be units long (since ).
The sine function is positive in the second quadrant. It is also equivalent to the side opposite the angle () divided by the hypotenuse ().
This makes .
Example Question #4 : How To Find The Sine Of An Angle
A sine function has a period of , a -intercept of , an amplitude of and no phase shift. These describe which of these equations?
Looking at this form of a sine function:
We can draw the following conclusions:
- because the amplitude is specified as .
- because of the specified period of since .
- because the problem specifies there is no phase shift.
- because the -intercept of a sine function with no phase shift is .
Bearing these in mind, is the only function that fits all four of those.
Example Question #1 : How To Find The Sine Of A Missing Side
In the triangle below, units and units. What is ?
Because , we need to first find the length of BC.
Using the Pythagorean theorem,
.
Example Question #3001 : Act Math
What is the value of in the triangle above? Round to the nearest hundredth.
We know that the sine of an angle is:
Therefore, we can write for this question:
This allows us to solve for easily:
Rounding, this gives us .
Example Question #1 : How To Find The Sine Of A Missing Side
A right triangle has leg lengths and . What is the sine of the angle opposite from the side of length ?
Using SOHCAHTOA, the sine of an angle is simply the length of the side opposite to it over the hypotenuse; however, we do not have the length of the hypotenuse yet.
Using the Pythagorean Theorem, we can solve for it:
So, the sine of this angle is:
Example Question #1 : How To Find An Angle With Sine
Simplify: (sinΘ + cosΘ)2
1 + sin2Θ
None of the answers are correct
cos2Θ -1
1 + cos2Θ
2sinΘcosΘ -1
1 + sin2Θ
Using the foil method, multiply. Simplify using the Pythagorean identity sin2Θ + cos2Θ = 1 and the double angle identity sin2Θ = 2sinΘcosΘ.
Example Question #1 : How To Find An Angle With Sine
For the triangle , find in degrees to the nearest integer
Note: The triangle is not necessarily to scale
None of the other answers
To solve this equation, it is best to remember the mnemonic SOHCAHTOA which translates to Sin = Opposite / Hypotenuse, Cosine = Adjacent / Hypotenuse, and Tangent = Opposite / Adjacent. Looking at the problem statement, we are given the side opposite of the angle we are trying to find as well as the hypotenuse. Therefore, we will be using the SOH part of our mnemonic. Inserting our values, this becomes . Then, we can write . Solving this, we get
Example Question #2 : How To Find An Angle With Sine
A fifteen foot ladder is leaned up against a twelve foot building, reaching the top of the building. What is the angle made between the ladder and the ground? Round to the nearest hundredth of a degree.
You can draw your scenario using the following right triangle:
Recall that the sine of an angle is equal to the ratio of the opposite side to the hypotenuse of the triangle. You can solve for the angle by using an inverse sine function:
or .
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