To find the height of a tree, a person walks to a point 30 feet from the base of the tree. She measures an angle of
between a line of sight to the top of the tree and the ground, as shown in
[link] . Find the height of the tree.
We know that the angle of elevation is
and the adjacent side is 30 ft long. The opposite side is the unknown height.
The trigonometric function relating the side opposite to an angle and the side adjacent to the angle is the tangent. So we will state our information in terms of the tangent of
letting
be the unknown height.
How long a ladder is needed to reach a windowsill 50 feet above the ground if the ladder rests against the building making an angle of
with the ground? Round to the nearest foot.
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Key equations
Cofunction Identities
Key concepts
We can define trigonometric functions as ratios of the side lengths of a right triangle. See
[link] .
The same side lengths can be used to evaluate the trigonometric functions of either acute angle in a right triangle. See
[link] .
We can evaluate the trigonometric functions of special angles, knowing the side lengths of the triangles in which they occur. See
[link] .
Any two complementary angles could be the two acute angles of a right triangle.
If two angles are complementary, the cofunction identities state that the sine of one equals the cosine of the other and vice versa. See
[link] .
We can use trigonometric functions of an angle to find unknown side lengths.
Select the trigonometric function representing the ratio of the unknown side to the known side. See
[link] .
Right-triangle trigonometry permits the measurement of inaccessible heights and distances.
The unknown height or distance can be found by creating a right triangle in which the unknown height or distance is one of the sides, and another side and angle are known. See
[link] .
Section exercises
Verbal
For the given right triangle, label the adjacent side, opposite side, and hypotenuse for the indicated angle.
the transfer of energy by a force that causes an object to be displaced; the product of the component of the force in the direction of the displacement and the magnitude of the displacement
A wave is described by the function D(x,t)=(1.6cm) sin[(1.2cm^-1(x+6.8cm/st] what are:a.Amplitude b. wavelength c. wave number d. frequency e. period f. velocity of speed.
A body is projected upward at an angle 45° 18minutes with the horizontal with an initial speed of 40km per second. In hoe many seconds will the body reach the ground then how far from the point of projection will it strike. At what angle will the horizontal will strike
Suppose hydrogen and oxygen are diffusing through air. A small amount of each is released simultaneously. How much time passes before the hydrogen is 1.00 s ahead of the oxygen? Such differences in arrival times are used as an analytical tool in gas chromatography.
the science concerned with describing the interactions of energy, matter, space, and time; it is especially interested in what fundamental mechanisms underlie every phenomenon
