Trigonometry Evaluations - Test Questions-ii

Question 21

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Question 22

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Question 23

Question:   Prove that sin 3q - sin q - sin 5q = sin 3q (1 - 2 cos 2q).

Answer:    LHS = sin 3q - (sin 5q + sinq)
= sin 3q - (2 cos 2q sin3q)
= sin 3q (1 - 2 cos 2q)

Question 24

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Question 25

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Question 26

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Question 27

Question:   Prove that cos 5^o - sin 25^o = sin 35^o.

Answer:   

=2sin30sin35

Question 28

Question:   Prove that cos 80^o + cos 40^o - cos 20^o = 0.

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Question 29

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Question 30

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