Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 4 - No. 12)
What is the value of cos(180° - θ) in terms of cos θ?
cos θ
-cos θ
sin θ
-sin θ
คำอธิบาย
In the second quadrant (180 - θ), cosine is negative. cos(180 - θ) = -cos θ.