This question is from trigonometry
Topic- Trigonometric ratios on. complementary angles
We have been asked to prove that cos54°cos36° – sin54°sin36° = 0 without using trigonometric tables
RS Aggarwal, Class 10, chapter 12, question no 3(ii)
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LHS = cos54° cos36° − sin54° sin36° = cos54°cos36° − sin(90° – 36°) sin(90° – 54°)
= cos54°cos36° – cos36°cos54°
= 0 = RHS