using cos(A-B)=cosA cosB+sinA sinB, find value of cos15°.
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cos(45°-30°)=cos45cos30+sin45sin30
=(1/√2)(√3/2)+(1/√2)(1/2)
=(√3/2√2) + (1/2√2)
=(√3 + 1)/(2√2)
=(1/√2)(√3/2)+(1/√2)(1/2)
=(√3/2√2) + (1/2√2)
=(√3 + 1)/(2√2)
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