MHB Problems involving Trigonometric Identities

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The discussion focuses on solving trigonometric identity problems involving right triangles. For the first problem, the tangent identities are used to derive equations for two triangles, ultimately solving for x. The second problem involves determining the slope of a line and calculating angles using arctan and the properties of triangles. The calculations yield the slope of a red line as 5.34, with a specific point provided for the equation. The conversation emphasizes the importance of understanding trigonometric identities and their applications in geometry.
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What are the step-by-step in solving these problems?
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For (1) I assume the lower left angle is a right angle. Then we have two right triangles. For the smaller right triangle, $tan(\theta)= \frac{5}{x}$. For the larger, $tan(\theta+ \alpha)= tan(2\theta)= \frac{5+ 8}{x}= \frac{13}{x}$.

For $tan(2\theta)$ you can use the identity $tan(2\theta)= \frac{2 tan(\theta)}{1- tan^2(\theta)}$.

Since the first equation says that $tan(\theta)= \frac{5}{x}$, the second says $\frac{\frac{10}{x}}{1- \frac{25}{x^2}}= \frac{13}{x}$ that you can solve for x.
 
For (2) the blue line is given by 6x+ 7y= 60 or y= -(6/7)x+ 60/7. Its slope is -6/7 so the "exterior angle" of that triangle is arctan(-6/7)= 139.4 degrees. The interior angle is 180- 139.4= 40.6 degrees. Since $\theta= 60$ degrees the third angle, where the red line crosses the base is 180- 60- 40.6= 120- 40.6= 79.4 degrees. So the slope of the red line is tan(79.4)= 5.34.
y= 5.34(x- x_0)+ y_0 where (x_0, y_0) is any point on the line. We are told that (3, 6) is such a point.
 
Country Boy said:
For (1) I assume the lower left angle is a right angle.

If not, the problem becomes quite messy ... 3 unknown sides & one unknown angle. I was able to come up with four equations, but I'll be damned if I would make a "by hand" attempt at solving them for x, y, & z.
 
Country Boy said:
For (2) the blue line is given by 6x+ 7y= 60 or y= -(6/7)x+ 60/7. Its slope is -6/7 so the "exterior angle" of that triangle is arctan(-6/7)= 139.4 degrees. The interior angle is 180- 139.4= 40.6 degrees. Since $\theta= 60$ degrees the third angle, where the red line crosses the base is 180- 60- 40.6= 120- 40.6= 79.4 degrees. So the slope of the red line is tan(79.4)= 5.34.
y= 5.34(x- x_0)+ y_0 where (x_0, y_0) is any point on the line. We are told that (3, 6) is such a point.
Got it! Thank You so much!
 
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