WAEC - Further Mathematics (2021 - No. 27)
If √5 cosx + √15sinx = 0, for 0° < x < 360°, find the values of x.
30° and 150°
150° and 210°
150° and 330°
210° and 330°
คำอธิบาย
√5 cosx + √15sinx = 0;
√5 (cosx + √3sinx) = 0
cosx = -sinx√3; \(\frac{sinx}{cos}\) = \(\frac{-1}{√3}\)
tanx = \(\frac{-1}{√3}\); x = 150° or 330°