Forward Kinematics of a Planar 2-Link Arm

Consider a planar 2-link revolute (RR) arm in the horizontal plane. Link lengths are $L_1 = 2$ m and $L_2 = 1$ m. The joint angles are $\theta_1 = 90^\circ$ (measured from the +x axis) and $\theta_2 = -90^\circ$ (measured relative to link 1, i.e. the standard relative-angle convention). The base joint is at the origin.

Using forward kinematics, compute the x-coordinate of the end-effector (the tip of link 2), in meters.

Recall: $x = L_1\cos\theta_1 + L_2\cos(\theta_1+\theta_2)$.