Ch 9 applies trigonometric ratios to solve real-world problems involving heights of buildings, towers, mountains, and distances across rivers — problems that cannot be measured directly.
Angle of elevation: angle formed by the line of sight with the horizontal when looking UP at an object. Angle of depression: angle formed when looking DOWN. The angle of depression from A to B equals the angle of elevation from B to A (alternate interior angles).
Draw a diagram with the right triangle. Identify the angle (elevation/depression). Use tan θ for height-distance problems, sin θ when hypotenuse is involved. Always mark all given information on the diagram.
Download: https://ncert.nic.in/textbook/pdf/jemh109.pdf | Complete book: https://ncert.nic.in/textbook/pdf/jemh1ps.zip
Angle of elevation is measured upward from the horizontal (when you look up at something). Angle of depression is measured downward from the horizontal (when you look down at something). They are numerically equal when the observer and object are connected by a direct line of sight.
Book a Trial + Diagnostic session. Get a personalized Learning Path with clear milestones, tutor match, and a plan recommendation — all within 24 hours.
Book Trial + Diagnostic →