trigonometry
posted by Yulieth .
tanθ= 2sqrt10/3 and π/2<θ< π find
a. cos(θ)
b. cos(11π/6  θ)
c.sin2θ
d.tanθ/2
can some please explain to me how to solve these questions? thanks

The angle is in the 2nd quadrant, so x is negative, and y is positive. The hypotenuse has length 7.
So, since tanθ = 2√10/3,
y = 2√10
x = 3
sinθ = y/h = 2√10/7
cosθ = x/h = 3/7
Use these values in your doubleangle, halfangle and sum/difference formulas