This is a free lesson from our course in Trigonometry
This lesson introduces trigonometric techniques for indirect measurement of tall
objects i.e. you wouldn't take a ruler or a tape to measure the distance or an angle. Note that this might seem complicated here in
text, but once you have instructor explain it to you in voice and handwriting in
the video, you will find it much simpler. In this you'll explore how the angles and sidelength properties of similar rightangled
triangles may be applied in measurement situations to calculate unknown side lengths
and angles. You can also use equivalent ratios to calculate the lengths of a triangle's sides: the height of an object or the length of a shadow. The next explanation focuses on the properties of similar isosceles rightangled triangles, where you use ratio in three pairs of similar isosceles rightangled triangles to find the unknown value on one triangle.
(More text below video...)
(Continued from above)
You can apply formulas to other parts of a triangle to determine or indirectly measure
a distance or an angle. For example, if an airplane measures the distances to two
battleships in the sea 910 m and 1000 m and the angle formed by the lines connecting
the ships to the plane is 47,
to find distance between two ships, you can use the formula b^{2} =
a^{2} + c^{2}  2ac cos B,
that yields the answer, b = 776.1 m.
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