Skip to main content
Super TutorResources
Chapter 25 of 28
QuestionsNotesFlashcardsSummaryFormulasQuizConceptsSyllabusPlan
Important Questions

Complementary Angles

ICSE · Class 9 · Mathematics

Most important questions from Complementary Angles for ICSE Class 9 Mathematics board exam 2026. MCQs, short answer, and long answer questions with marks.

41 questions28 flashcards5 concepts

Interactive on Super Tutor

Studying Complementary Angles? Get the full interactive chapter.

Quizzes, flashcards, AI doubt-solver and a step-by-step study plan — built for important questions and more.

Try Super Tutor — Free

1,000+ Class 9 students started this chapter today

An illustration showing two acute angles whose sum is 90 degrees, defining them as complementary angles. Examples like 30 and 60 degrees, and a general case with x and (90-x) degrees.
Super Tutor

Learn better with visuals Super Tutor has hundreds of illustrations like this across every chapter — all free to try.

Get started
41 Questions·
multiple choicemultiple correcttext answer

Sample Questions

1multiple correct

Which of the following are equal to tan 40°?

Show answer

cot 50°, cot(90° - 40°), sin 40°/cos 40°, cos 50°/sin 50°

tan 40° = cot(90° - 40°) = cot 50°. Also, tan 40° = sin 40°/cos 40°. Since 40° and 50° are complementary, cos 50° = sin 40° and sin 50° = cos 40°, so cos 50°/sin 50° = sin 40°/cos 40° = tan 40°.

2multiple choice

Calculate: tan 45° × cot 45°

Show answer

1

We know that tan 45° = 1 and cot 45° = 1. Therefore, tan 45° × cot 45° = 1 × 1 = 1. Alternatively, since cot θ = 1/tan θ, we have tan θ × cot θ = 1 for any angle θ (except where undefined).

3multiple correct

Which of the following statements are true?

Show answer

sin 30° = cos 60°, tan 45° = cot 45°, sec 70° = cosec 20°

For complementary angles: sin 30° = cos(90° - 30°) = cos 60° ✓. tan 45° = cot 45° = 1 ✓. sec 70° = cosec(90° - 70°) = cosec 20° ✓. However, sin 40° ≠ cos 40° since they're equal only when the angle is 45°.

4multiple choice

Find the value of: cos 0° + cos 30° + cos 60° + cos 90°

Show answer

1 + √3/2 + 1/2 + 0

cos 0° = 1, cos 30° = √3/2, cos 60° = 1/2, cos 90° = 0. Therefore, the sum = 1 + √3/2 + 1/2 + 0 = 3/2 + √3/2 = (3 + √3)/2.

+37 more questions available

Practice All

Frequently Asked Questions

What are the important topics in Complementary Angles for ICSE Class 9 Mathematics?
Complementary Angles covers several key topics that are frequently asked in ICSE Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Complementary Angles — ICSE Class 9 Mathematics?
Understand the core concepts first, then work through the 41 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
How many important questions are there in Complementary Angles?
There are 41 practice questions available for Complementary Angles. These cover multiple question types including MCQs, short answer, and long answer questions.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for Complementary Angles

All 28 chapters — ICSE Class 9 Mathematics Important Questions

For serious students

Get the full Complementary Angles chapter — for free.

Quizzes, flashcards, AI doubt-solver and a step-by-step study plan for ICSE Class 9 Mathematics.

Try Super Tutor Free
Try the full chapter — Free