(cos75°+sin75°)(cos75°-sin75°)

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(cos75°+sin75°)(cos75°-sin75°)(cos75°+sin75°)(cos75°-sin75°)(cos75°+sin75°)(cos75°-sin75°)(cos75°+si

(cos75°+sin75°)(cos75°-sin75°)
(cos75°+sin75°)(cos75°-sin75°)

(cos75°+sin75°)(cos75°-sin75°)
(cos75°+sin75°)(cos75°-sin75°)
=cos²75º-sin²75º
=cos150º
=cos(180º-30º)
=-cos30º
=-√3/2

(cos75°+sin75°)(cos75°-sin75°)
=(cos75)^2-(sin75)^2
=cos(2*75)
=cos150
=-cos30
=-根号3/2

(cos75°+sin75°)(cos75°-sin75°)
=cos150°
=-√3\2