Trigonometry
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SAT Math › Trigonometry
A right triangle has an acute angle $\theta$. The side adjacent to $\theta$ is 9 and the hypotenuse is 15. What is $\cos(\theta)$?
$\frac{3}{5}$
$\frac{9}{15}$
$\frac{5}{3}$
$\frac{15}{9}$
Explanation
The question requires finding cos(θ) in a right triangle where the side adjacent to acute angle θ is 9 and the hypotenuse is 15. According to SOH-CAH-TOA, cosine is the ratio of adjacent over hypotenuse, so cos(θ) = adjacent / hypotenuse. Set up the ratio as cos(θ) = 9 / 15. Simplify 9/15 to 3/5. A key error to avoid is mixing up adjacent and opposite sides, which might lead to using sine instead. For test-taking, double-check the side identifications relative to the given angle before selecting the ratio.
In right triangle $\triangle MNO$, $\angle O=90^\circ$ and $\angle M=48^\circ$. If the side opposite $\angle M$ is 17, what is the hypotenuse (to the nearest tenth)?
11.4
17.0
22.9
25.4
Explanation
This asks for the hypotenuse in right triangle MNO with right angle at O, angle M at 48 degrees, and opposite side 17, to the nearest tenth. Sine is opp/hyp from SOH-CAH-TOA. Set up sin(48°) = 17 / hypotenuse. Solve hypotenuse = 17 / sin(48°) ≈ 17 / 0.7431 ≈ 22.87, rounding to 22.9. Using cosine mistakenly requires adjacent side. Ensure precise sine values for accurate rounding.
In the coordinate plane, points $A(0,0)$, $B(6,0)$, and $C(6,8)$ form a right triangle with a right angle at $B$. What is the measure of $\angle A$ (to the nearest degree)?
$37^\circ$
$67^\circ$
$53^\circ$
$60^\circ$
Explanation
The question requires the measure of angle A at (0,0) in right triangle ABC with points B(6,0), C(6,8), right at B, to the nearest degree. Tangent applies with opposite BC=8 and adjacent AB=6 relative to A via SOH-CAH-TOA. Set up tan(A) = 8 / 6 ≈ 1.333. Calculate A = tan⁻¹(1.333) ≈ 53.13 degrees, rounding to 53 degrees. Confusing coordinates might lead to wrong sides, but plot points to confirm. Verify with other ratios like sine for consistency.
A right triangle has an acute angle $\theta$ with opposite side 16 and adjacent side 30. What is $\theta$ to the nearest degree?
$28^\circ$
$62^\circ$
$33^\circ$
$57^\circ$
Explanation
This problem asks for acute angle θ to the nearest degree in a right triangle with opposite side 16 and adjacent side 30. Tangent is opposite over adjacent per SOH-CAH-TOA. Set up tan(θ) = 16 / 30 ≈ 0.5333. Calculate θ = tan⁻¹(0.5333) ≈ 28.07 degrees, rounding to 28 degrees. A mistake is using hypotenuse, but it's not given. Calculate hypotenuse to check if ratios match.
Right triangle $\triangle JKL$ has $\angle K=90^\circ$, $JK=14$, and hypotenuse $JL=20$. What is the measure of $\angle J$ (to the nearest degree)?
$34^\circ$
$44^\circ$
$46^\circ$
$56^\circ$
Explanation
The question seeks the measure of angle J in right triangle JKL with right angle at K, JK = 14, and hypotenuse JL = 20, to the nearest degree. Cosine is adj/hyp from SOH-CAH-TOA, with JK adjacent to J. Set up cos(J) = 14 / 20 = 0.7. Then, J = cos⁻¹(0.7) ≈ 45.57 degrees, rounding to 46 degrees. Errors occur if opposite is used instead of adjacent. Compute the missing side to verify consistency.
A drone ascends along a straight path that makes a $25^\circ$ angle with the ground. After traveling 120 m along this path, how high is the drone above the ground (to the nearest meter)?
51 m
254 m
109 m
283 m
Explanation
The question finds the height of a drone after ascending 120 meters at a 25-degree angle with the ground, to the nearest meter. Sine is appropriate as height is opposite the angle and path is hypotenuse via SOH-CAH-TOA. Set up sin(25°) = height / 120. Calculate height = 120 × sin(25°) ≈ 120 × 0.4226 = 50.712, rounding to 51 meters. Using tangent incorrectly assumes horizontal distance given. Verify the given length is hypotenuse for sine.
In right triangle $\triangle DEF$, $\angle F=90^\circ$. If $\angle D=62^\circ$ and $DF=9$ (adjacent to $\angle D$), what is $EF$ (to the nearest tenth)?
4.2
9.0
16.9
17.0
Explanation
This asks for EF in right triangle DEF with right angle at F, angle D at 62 degrees, and adjacent DF = 9, to the nearest tenth. Tangent fits as EF is opposite and DF adjacent to D per SOH-CAH-TOA. Set up tan(62°) = EF / 9. Calculate EF = 9 × tan(62°) ≈ 9 × 1.8807 = 16.926, rounding to 16.9. Confusing with cosine would find hypotenuse instead. Sketch to confirm opposite vs. adjacent.
A right triangle has legs 8 and 15. Let $\theta$ be the acute angle adjacent to the 15-unit leg and opposite the 8-unit leg. What is $\tan(\theta)$?
$\frac{15}{17}$
$\frac{8}{17}$
$\frac{8}{15}$
$\frac{15}{8}$
Explanation
The problem requires tan(θ) in a right triangle with legs 8 and 15, where θ is adjacent to 15 and opposite 8. Tangent is opposite over adjacent from SOH-CAH-TOA. Set up tan(θ) = 8 / 15. The hypotenuse is sqrt(8² + 15²) = 17, but unnecessary here. Errors include using hypotenuse, giving sin or cos instead. Identify sides precisely relative to θ before ratio selection.
From a point on the ground, the angle of elevation to the top of a flagpole is $54^\circ$. The point is 18 m from the base. How tall is the flagpole (to the nearest tenth)?
13.1 m
24.8 m
30.6 m
10.6 m
Explanation
This question finds the height of a flagpole with a 54-degree angle of elevation from 18 meters away, to the nearest tenth. Tangent applies as height is opposite and distance adjacent to the angle per SOH-CAH-TOA. Set up tan(54°) = height / 18. Calculate height = 18 × tan(54°) ≈ 18 × 1.3764 = 24.775, rounding to 24.8 meters. Using sine mistakenly treats distance as hypotenuse. Confirm no hypotenuse is involved for tangent problems.
A right triangle has acute angles $\theta$ and $\phi$ (so $\theta+\phi=90^\circ$). If $\sin(\theta)=0.6$, what is $\cos(\phi)$?
0.4
0.6
0.8
1.6
Explanation
The problem seeks cos(φ) given sin(θ) = 0.6, where θ and φ are complementary acute angles in a right triangle. Since φ = 90° - θ, cos(φ) = sin(θ) by cofunction identity. Thus, cos(φ) = 0.6. Using SOH-CAH-TOA directly, sin(θ) means opposite/hypotenuse for θ is adjacent/hypotenuse for φ. A common error is thinking cos(φ) = cos(θ), but remember complementary relationships. This highlights using identities for related angles.