Helen's Holiday Blog #4

9-1

Examples:

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

cos70=a/20

a=20cos70=6.840ft

sin70=b/20

b=20sin70=18.794ft


2) The highest tower in the world is in Toronto, Canada and is 553m high. An observer at point A, 100m from the center of the tower's base, sights the top of the tower, the angle of elevation is angle A. Find the measure of this angle to the nearest tenth of degrees.

tan A=553/100

A=tan inverse (553/100)=79.750 degrees


9-2

Formulas: 1/2 bh for right angles only or 1/2 ab sin(angle b/w) for non right angles

Examples:

1) Two sides of a triangle have lengths 7cm and 4cm. The angle between the sides measures 73 degrees. Find the area of the triangle.

A=1/2ab sin (theta)
A=1/2(7)(4)sin(73)
A=1/2(28)sin73
=14 sin 73
=13.388