Grade 10 Cosine Law Worksheets
Start with eight focused practice problems, then use the answer key below to check the worksheet.
Practice Worksheet
Grade 10 Cosine Law Practice
Solve each problem. Show your work.
- 1.In triangle ABC, a = 10 cm, b = 10 cm, and included angle C = 44°. Find side c. Round sides to 1 decimal place.
- 2.In triangle ABC, a = 9 cm, b = 16 cm, and included angle C = 106°. Find side c. Round sides to 1 decimal place.
- 3.In triangle ABC, a = 18 cm, b = 11 cm, and included angle C = 73°. Find side c. Round sides to 1 decimal place.
- 4.In triangle ABC, a = 10 cm, b = 8 cm, and included angle C = 109°. Find side c. Round sides to 1 decimal place.
- 5.In triangle ABC, a = 13 cm, b = 11 cm, and included angle C = 79°. Find side c. Round sides to 1 decimal place.
- 6.In triangle ABC, a = 16 cm, b = 17 cm, and included angle C = 93°. Find side c. Round sides to 1 decimal place.
- 7.In triangle ABC, a = 13 cm, b = 11 cm, and included angle C = 85°. Find side c. Round sides to 1 decimal place.
- 8.In triangle ABC, a = 7 cm, b = 18 cm, and included angle C = 51°. Find side c. Round sides to 1 decimal place.
Show answer key
- Question 1: 7.5 cm
- Question 2: 20.4 cm
- Question 3: 18.1 cm
- Question 4: 14.7 cm
- Question 5: 15.3 cm
- Question 6: 23.9 cm
- Question 7: 16.3 cm
- Question 8: 14.6 cm
Next Steps
Finished the worksheet? Get it checked in seconds
Snap a photo of your child's completed Grade 10 cosine law work and Gradulo checks every answer with step-by-step feedback.
Check my workNeed another worksheet?
Log in to generate more Grade 10 cosine law worksheets and keep practice going.
About These Worksheets
Grade 10 students use cosine law for oblique triangle problems that do not provide a sine-law matching pair.
Cosine law worksheets help Grade 10 students solve non-right triangles when the sine law does not fit. The cosine law is used when two sides and the included angle are known, or when all three sides are known and an angle must be found. Students learn to choose this tool by looking at the pattern of given information before substituting into a formula.
These worksheets include missing side questions, missing angle questions, and applications such as navigation, construction, and indirect measurement. Students practise careful substitution, squaring side lengths, rearranging for an unknown angle, and using inverse cosine. The cosine law is algebraically heavier than SOHCAHTOA or sine law, so organized work matters. It strengthens both trigonometry and equation-solving skills.
Skills Practised
- Recognizing side-angle-side and side-side-side situations
- Using cosine law to find a missing side
- Rearranging cosine law to find a missing angle
- Substituting values accurately into the formula
- Checking whether an answer is reasonable from the diagram
Parent Tip: Cosine law is hard to audit casually. Compare the answer key, then use photo checking if your teen's setup has several squared terms or a rearranged formula.