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Law of Sines Worksheet with Answers – Precalculus (Free PDF)

Last updated: October 22, 2026 · Written by the Math Made Easy math teachers

Precalculus Math Worksheets – Mathbot, the Math Made Easy robot coach, with free printable worksheets for Precalculus

These 20 problems cover triangle area, Heron’s formula, the Law of Sines, the Law of Cosines, the ambiguous SSA case and navigation with bearings. They train standards G-SRT.D.9, G-SRT.D.10 and G-SRT.D.11.

The last six problems use a pond, two ranger stations, a hiker, a lot and a garden with two possible shapes.

Standards: G-SRT.D.9, G-SRT.D.10, G-SRT.D.11 · Level: Grade 12 Precalculus

Problem 2 Heron’s Formula ★★★

Use Heron’s formula to find the area of a sail with sides 20, 37 and 51 inches.

Problem 3 Law of Sines with AAS ★★★

In triangle ABC, A = 48°, B = 71° and a = 12. Find C, b and c to the nearest hundredth.

Problem 4 Law of Cosines for the Third Side ★★★

In triangle ABC, a = 8, b = 11 and C = 52°. Find c to the nearest hundredth.

Problem 5 Third Side from a Figure ★★★

In the figure, sides 7 and 9 meet at A with an angle of 64°. Find the length of the third side to the nearest hundredth.

ABCa = ?79
The angle at A is 64°; sides AC = 7 and AB = 9.

Problem 6 Angle from Three Sides ★★★

A triangular plot has sides 8, 10 and 15 yards. Find its largest angle to the nearest tenth of a degree.

Problem 7 Law of Sines with ASA ★★★

In triangle ABC, A = 36°, C = 79° and side b = 20. Find B, a and c to the nearest hundredth.

Problem 8 SSA with One Triangle ★★★

In triangle ABC, A = 50°, a = 15 and b = 11. Find B, C and c.

Problem 9 SSA with No Triangle ★★★

Can a triangle have A = 40°, a = 5 and b = 9? Justify your answer.

Problem 10 SSA with Two Triangles ★★★

Triangle ABC has A = 32°, a = 9 and b = 13. Show that two triangles fit, and solve both for B, C and c (one decimal place). The figure shows the idea for similar data.

ACB₁B₂b = 10a = 630°
Angle A = 30°, b = 10 and a = 6 fit two triangles.

Problem 11 Ship on Two Bearings ★★★

A ship sails 20 miles on a bearing of 040°, then 15 miles on a bearing of 115°. How far is it from its starting point? Round to the nearest tenth.

NN20 mi, 040°15 mi, 115°start
Path of the ship.

Problem 12 Area from Three Decimal Sides ★★★

Find the area of a triangle with sides 7.2, 8.5 and 10.1 centimeters, to the nearest tenth.

Problem 13 Find the Area After Solving ★★★

In triangle ABC, A = 52°, B = 63° and a = 10. Find side b, angle C and the area, rounded to the nearest tenth.

Problem 14 Area of a Parallelogram ★★★

A parallelogram has sides 12 and 18 and an included angle of 65°. Use triangle area to find its area to the nearest tenth.

Problem 15 All Three Angles from Three Sides ★★★

A triangle has sides 12, 15 and 20. Find all three angles to the nearest tenth of a degree.

Problem 16 Distance Across a Pond ★★★

Points A and B are on opposite sides of a pond. From point C, CA = 210 feet, CB = 165 feet and angle ACB = 74°. Find the distance AB.

CAB
Triangle across the pond: CA = 210 ft, CB = 165 ft, angle C = 74°.

Problem 17 Locating a Fire from Two Stations ★★★

Two ranger stations A and B are 8.4 miles apart. A fire F is sighted at an angle of 62° from the line AB at station A and 48° at station B. How far is the fire from each station?

Problem 18 Hiker Back to Camp ★★★

A hiker walks 3.5 miles on a bearing of 025°, then 2.2 miles on a bearing of 140°. How far is she from camp, and what angle does her straight-line path back make with her first leg at the start? Round to the nearest tenth of a mile and degree.

Problem 19 Triangular Lot ★★★

A triangular lot has sides 120, 150 and 190 feet. Find its area, then the cost of sod at $0.85 per square foot.

Problem 20 A Garden with Two Possible Shapes ★★★

A triangular garden has angle A = 28°, side AC = 18 feet and side BC = 11 feet. Show that two shapes are possible, and find the length AB and the area for each (one decimal place).

View the Law Of Sines worksheet answer key

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