Nathan's Blog

I will go over the notes from chapter 9, which involved right triangles. I understood section 9-1 really well.

sin(theta)=opposite/hypotenuse
cos(theta)=adjacent/hypotenuse
tan(theta)=opposite/adjacent
csc(theta)=hypotenuse/opposite
sec(theta)=hypotenuse/adjacent
cot(theta)=adjacent/opposite
An easy way to remember all of this is SOCAHTOA.

These functions are only to be used when dealing with right triangles. The hypotenuse is opposite of the right angle.

I will give a word problem example.

The safety instructions for a 20 ft. ladder indicate that the ladder should not be inclined at more than a 70 degree angle with the ground. Suppose the ladder is leaned against a house at this angle. Find the distance from the base of the house to the foot of the ladder and the height reached by the ladder.

Draw a triangle with a 70 degree angle and a 20 ft. hypotenuse. Then you draw a little house next to it. Little a is the distance on the ground and little b is the height.

So you get:
cos70 degrees=a/20
a=20cos70=6.840 ft.

For b:
sin70=b/20
b=20sin70=18.794 ft.

That is basically it for 9-1. It was an easy section.