prove that cos (72 +ø) =sin (18-ø)
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Answer:
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Step-by-step explanation:
cos18
o
sin12
o
+sin18
o
cos72
o
= cos(90
o
–72
o
)sin72
o
+sin(90
o
–72
o
)cos72
o
= sin72
o
.sin72
o
+cos72
o
cos72
o
=sin
2
72
o
+cos
2
72
o
=1
(∵sin
2
θ+cos
2
θ)
hopefully I helped
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