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Question
Evaluate the following:
sin 10° – cos 80°
Evaluate
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Solution
Given: sin 10° – cos 80°
Step-wise calculation:
1. Use the co-function identity cos θ = sin (90° – θ).
So, cos 80° = sin (90° – 80°)
= sin 10°
2. Substitute:
sin 10° – cos 80°
= sin 10° – sin 10°
= 0
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Chapter 18: Trigonometric Ratios of Some Standard Angles and Complementary Angles - Exercise 18C [Page 380]
