3. El ángulo \( \frac{2}{5} \) mrad equivale en grados a \( \begin{array}{llll}\text { A. } 30^{\circ} & \text { B. } 36^{\circ} & \text { C. } 72^{\circ} & \text { D. } 108^{\circ}\end{array} \)

For what values of the angle between \( \vec{A} \) and \( \vec{B} \) will the dot product \( \vec{A} \vec{B} \) be positive, negative or zero?

ind \( \tan ^{-1}(-\sqrt{3}) \)

4 ¿Cuál es el valor del ángulo absoluto del vector? (Escriba solo el valor, sin la unidad \( { }^{\circ} \) ) * \( \vec{b}=6.8 \mathrm{Km}, 83^{\circ} \) al SOe

d) \( \frac{\sin \theta}{1-\cos \theta}-\frac{1+\cos \theta}{\sin \theta}=0 \quad \checkmark \checkmark \checkmark \checkmark \checkmark \)

3. Prove \( \sin 3 x=3 \cos ^{2} x \sin x-\sin ^{2} x \) 4. Prove \( \sec 2 x=\frac{\csc ^{2} x}{\csc ^{2} x-2} \) 5. Prove \( \frac{1+\cos \theta}{\sin \theta}+\frac{\sin \theta}{1+\cos \theta}=2 \csc \theta \) 6. Prove \( \frac{c s c^{2} \theta-1}{c s^{2} \theta}=\cos ^{2} \theta \) 7. Prove \( \frac{1}{1-\cos ^{2}}+\frac{1}{1+\cos \mathrm{B}}=2 \csc ^{2} \) 8. Prove \( \left(\cot ^{2} A+1\right)\left(\sin ^{2} A-1\right)=-\cot ^{2} A \)