Answer: 17 -3n
Explanation:
In the given arithmetic progression 20,17,14,11,8....
first term that is a = 20
common difference that is d= a2-a1 = 17-20 = -3
let n is the nth term
= a+(n-1)d
substituting the values of first, common,difference and n
=20+(n-1) (-3)
= 20 -3n+3
=23 -3n
Hints on solving trigonometry problems:
If no diagram is given, draw one yourself.
Mark the right angles in the diagram.
Show the sizes of the other angles and the lengths of any lines that are known
Mark the angles or sides you have to calculate.
Consider whether you need to create right triangles by drawing extra lines. For example, divide an isosceles triangle into two congruent right triangles.
Decide whether you will need Pythagorean theorem, sine, cosine or tangent.
Check that your answer is reasonable. The hypotenuse is the longest side in a right triangle.
How to use the tangent ratio to find missing sides or angles?
Example:
