Posted by **Yulieth** on Sunday, November 20, 2011 at 7:18pm.

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

- trigonometry -
**Steve**, Sunday, November 20, 2011 at 10:55pm
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 double-angle, half-angle and sum/difference formulas

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