Question

Find the value of: cos(theta-pi)​

Answer 1

cos(π + θ) = -cosθ, tan(π + θ) = +tanθ, cot(π + θ) = +cotθ. Connecting the M that is in the 3rd Quadrant to O and extending it to cross the tangent and cotangent axes, it crosses them in their positive region, and hence, both are positive for angle π + θ.