How do you find the exact value of cos(pi/3)cos(5pi/12)-sin(pi/3)sin(5pi/12)?

Question

How do you find the exact value of cos(pi/3)cos(5pi/12)-sin(pi/3)sin(5pi/12)?

Md Ariful Islam

বিএসসি(সিএসই) , এমবিএ(মার্কেটিং)

সফটওয়্যার ইঞ্জিনিয়ার Bissoy.com

4 views

2025-01-04 04:42

1 Answers

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score 0 · Accepted Answer · 2024-04-02T09:48:30+06:00

Md Ariful Islam

বিএসসি(সিএসই) , এমবিএ(মার্কেটিং)

সফটওয়্যার ইঞ্জিনিয়ার Bissoy.com

Apply the trig identity:
cos a.cos b - sin a.sin b = cos (a + b)
$cos (pi/3).cos ((5pi)/12) - sin ((5pi)/12).sin (pi/3) = $
$= cos (pi/3 + (5pi)/12) = cos ((9pi)/12) = cos ((3pi)/4) = -sqrt2/2$

4 views Answered 2024-04-02 09:48