Same chapter3 marksDifficulty: Medium
If tan θ = 3/4, find sin θ and cos θ for an acute angle θ.
Trigonometrical Ratios
3 marksDifficulty: Medium
Prove that sin2θ + cos2θ = 1 for an acute angle θ.
Original Khojo Papers practice question — not from a past board paper.
Answer
In a right-angled triangle with opposite side a, adjacent side b and hypotenuse c, sin θ = a/c and cos θ = b/c. So sin2θ + cos2θ = (a2 + b2)/c2, and by the Pythagoras theorem a2 + b2 = c2, so the value is 1.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
The identity therefore rests entirely on the Pythagoras theorem.
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