Prove that sin 65° cos 20° − cos 65° sin 20° = 1√2
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Answer:
sin65
o
+cos65
o
=sin(45
o
+20
o
)+cos(45
o
+20
o
)
=sin45
o
cos20
o
+cos45
o
sin20
o
+cos45
o
cos20
o
−sin45
o
sin20
o
=
2
cos20
o
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