1. Let us evaluate:

2. Let us show that:

2.

3. If two angles α and β are complementary angles, let us show that

4. If sin 17^{o} = x/y, let us show that ;

5. let us show that;

6. ∠A + **∠**B =90^{o}, let us show that ;

7. let us show that ;

8. If **∠**P + **∠**Q = 90^{o}, let us show that ;

9. let us prove that ;

10. AOB is a diameter of a circle with center O and C is any point on the circle, joining A.C, B,C and O,C let us show that;

10.

11. ABCD is a rectangular figure, joining A, C let us prove that.