Height of Pyramid from Two Angles and Side

geometrytrigonometry

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Full Disclosure: I am a high school student.

Suppose that I have a right triangular pyramid, with triangle BCD being the base and A being the top point. D is a right angle. Angle ABD = 37deg, angle ACD = 32deg. What is the height of AD (the height of the pyramid)? Thanks!

I managed to get three equations and combine them, but each time I do that, it proves that 1=1 or that a side is = to a side, which is useless.

Best Answer

Let $a=BD$, $b=CD$.

$$a^2+b^2=108^2 \tag{1}$$

$$h=b \tan 32° \tag{2}$$

$$h=a \tan 37° \tag{3}$$

Therefore $a \tan 37°=b \tan32°$ ($h$ has been eliminated, getting

$$a=b \dfrac{\tan 32°}{\tan 37°}$$

You have now a second equation with $a$ and $b$ only, that you can combine with (1) to obtain $b$ for example as a solution a quadratic equation.

Then in a second step, you will obtain $h$ from (2) for example.

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