- A
- B
- C
- D
Step-by-Step Solution
The right angle is at , so is the hypotenuse. For angle , the side opposite is and the side adjacent (other than the hypotenuse) is . tan = opposite/adjacent = .
Answer: D)
In right triangle ABC the right angle is at C. Which ratio of sides equals tan B?
Class 10Introduction to TrigonometryTrigonometry
Key idea: Why ratios — and not lengths
Two right triangles with the same acute angle θ are SIMILAR (Class 10 ch. 6 — AA criterion: both have a right angle and the angle θ).
Similar triangles → corresponding sides in fixed ratio.
So the ratio (opposite / hypotenuse) takes the SAME value in any right triangle with angle θ — regardless of how big the triangle is.
That's why sin θ, cos θ, tan θ are FUNCTIONS of the angle alone — they're well-defined.
This is the fundamental reason trigonometry works as a clean theory.
Similar triangles → corresponding sides in fixed ratio.
So the ratio (opposite / hypotenuse) takes the SAME value in any right triangle with angle θ — regardless of how big the triangle is.
That's why sin θ, cos θ, tan θ are FUNCTIONS of the angle alone — they're well-defined.
This is the fundamental reason trigonometry works as a clean theory.
Master this chapter in 30 minutes a day.
Don't just memorise the answer — build a daily practice habit.
Practice 5 Similar Questions Free →All Introduction to Trigonometry practice questions
More Class 10 Introduction to Trigonometry practice
In a right triangle the side opposite an acute angle θ is 20 cm and the hypotenuse is 29…A rectangle is 8 cm long and 6 cm wide. Its diagonal makes an angle θ with the longer…A right triangle has its two legs equal in length. For one of its acute angles θ, what…If cot θ = 8/15 for an acute angle θ, find sec θ.If sec θ = 2 for an acute angle θ, find tan θ.