for all values of θ , the values of 3−cosθ +cos(θ+π3) lie in the interval
[-2,3]
[-2,1]
[2,4]
[1,5]
Let y=3−cosθ+cos(θ+π3)=3+2sin(θ+π6)sin(−π6)=3−sin(θ+π6)⇒−≤−sin(θ+π6)≤1⇒3−1≤3−sin(θ+π6)≤3+1⇒2≤y≤4∴y∈[2,4]
Some trigonometric ratios and the interval in which θ lies is given. Match the intervals with the ratios which are positive in those intervals.
θ gives positive values
p. (0, π2) 1. Only sin θ, cosecθ
q. (π2, π) 2. Only cosθ, secθ
r. (π,3π2) 3. Only tanθ, cotθ
s. (3π2,2π) 4. All sinθ, cosθ, tanθ, cotθ, secθ, cosecθ
In the table, trigonometric ratios and the intervals of θ are given. Match the intervals with the ratios which are positive in those intervals.