( sin 72° + cos 18°) (sin 72 - cos 18)
please solve it with explanation
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Answered by
1
Answer:
(sin 72˚ + cos 18˚)(sin 72˚ – cos 18˚)
= [sin (90˚ – 18˚) + cos 18˚][sin (90˚ – 18˚) – cos 18˚]
= [cos 18˚ + cos 18˚][cos 18˚ – cos 18˚]
= 0
Answered by
1
Cos18 = Cos(90-72)
Cos18 = Sin72
Because 90 wil change cos into sin and it is in first quadrant so no sign change
Cos18 = Sin72
Because 90 wil change cos into sin and it is in first quadrant so no sign change
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