This is the basic and conceptual question from trigonometry(trignometric ratios) in which we have been asked to find the value of cos 45° cos 30° + sin 30° sin 45°
RS Aggarwal, class 10, chapter 11, question no 3.
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We know that,
cos45∘ = 1/√2 = sin45∘
cos30∘= √3/2 and
sin30∘ = 1/2
Now,
cos45∘cos30∘+sin45∘sin30∘
= 1/√2×√3/2 + 1/√2×1/2
= √3/2√2 + 1/2√2
cos45∘cos30∘ + sin45∘sin30∘
= (√3+1)/2√2