defence exam Coast Guard Navik GD (General Duty) 02/2025 Mock Test Series Mathematics Trigonometry Trigonometric Functions
If \(\tan \alpha=\frac{1}{7}\), \(\sin \beta=\frac{1}{\sqrt{10}}\); \(0<\alpha, \beta<\frac{\pi}{2}\), then what is the value of cos (α + 2β) ?
1
\(-\frac{1}{2}\)
2
\(-\frac{1}{\sqrt{2}}\)
3
\(\frac{1}{\sqrt{2}}\)
4
\(\frac{1}{2}\)