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Sati [7]
2 years ago
12

Prove that:cos20°cos40°cos80°=1/8​

Mathematics
2 answers:
Naya [18.7K]2 years ago
7 0

Answer:

see explanation

Step-by-step explanation:

Using the double angle identity for sine

sin2x = 2sinxcosx

Consider left side

cos20°cos40°cos80°

= \frac{1}{2sin20} (2sin20°cos20°)cos40°cos80°

= \frac{1}{4sin20} (2sin40°cos40°)cos80°

= \frac{1}{4sin20} (sin80°cos80° )

= \frac{1}{8sin20} (2sin80°cos80° )

= \frac{1}{8sin20} . sin160°

= \frac{1}{8sin20} . sin(180 - 20)°

= \frac{1}{8sin20} . sin20°

= \frac{1}{8} = right side , thus proven

viva [34]2 years ago
7 0

Step-by-step explanation:

hope its helps you have a great day keep smiling be happy stay safe ☺

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