Analysis and Approaches for IBDP Maths Ebook 1 | Page 94

Your Practice Set – Analysis and Approaches for IBDP Mathematics
32
Paper 1 Section A – Finding trigonometric
ratios by trigonometric identities
Example
Let
cos� �
7
, where � is acute.
4
(a) Find sin� .
(b) Find sin 2� .
[3]
[2]
Solution
(a)
(b)
sin�
2
� 1� cos �
(M1) for using identity
2
� 7 �
� 1�� �
4 �
(A1) for substitution
� �
3
� A1 N2
4
sin 2�
� 2sin�cos�
�3�� 7 �
� 2� � � 4
�� 4 �
�� �
(A1) for substitution
3 7
� A1 N2
8
[3]
[2]
Exercise 32
1. Let
2
sin� � , where � is acute.
3
(a) Find cos� .
(b) Find sin 2� .
[3]
[2]
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