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TS EAMCET · Maths · Trigonometric Ratios & Identities

Let ACB be a triangle with right-angle at C. Let AB=29 units, BC=21 units and ABC=θ. Then cos2θ-sin2θ=

  1. A 1
  2. B 41841
  3. C 40441
  4. D 41800
Verified Solution

Answer & Solution

Correct Answer

(B) 41841

Step-by-step Solution

Detailed explanation

△ACB is a right triangle, right angled at C. Therefore, by using Pythagoras theorem we get, AB2=AC2+BC2 AC2=AB2-BC2 AC2=292-212 AC2=400 AC=20 units cos θ=BCAB=2129 sin θ=ACAB=2029 ⇒cos2θ-sin2θ=21292-20292=41841