The value of cos 3 π 8 . cos 3 π 8 + sin 3 π 8 . sin 3 π 8 is:

The value of cos3π8.cos3π8+sin3π8.sin3π8 is:
  1. 12
  2. 122
  3. 12
  4. 14

Solution

⇒cos3π8cosπ2-π8+sin3π8sinπ2-π8

⇒cos3π8sinπ8+sin3π8cosπ8

⇒sinπ8cosπ8sin2π8+cos2π8

⇒12sinπ4

⇒122

Asked in: JEE Main 2020 (09 Jan Shift 1)

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