If $∆ABC$ is right-angled at C, then the value of cos (A + B) is

1.  0

2.  1

3.  $\frac{1}{2}$

4.  $\frac{\sqrt{3}}{2}$

If a vector is inclined at angles, $\mathrm{\alpha }, \mathrm{\beta }, \mathrm{and} \mathrm{\gamma }$ with x, y, and z-axis respectively, then the value of ${\sin }^2 \mathrm{\alpha } + {\sin }^2 \mathrm{\beta }+ {\sin }^2 \mathrm{\gamma }$ is equal to

1. 0

2. 1

3. 2

4. $\frac{1}{2}$

What is the maximum value of 5sinθ – 12cosθ?

1.  12

2.  17

3.  7

4.  13

Which of the following is not possible?
1. sin θ = \(3\over5\)
2. sec θ = 100
3. cosec θ = 0.14
4. None of the above