Here, we are given with two sides and the triangle is a right angled triangle. Here, we can use trigonometry to find the missing angle.
- Note: Always remember that the perpendicular, base and hypotenuse changes with the reference angle.
According to missing angle, cos theta can be used because we are given with base and hypotenuse. No need to find the perpendicular.
[tex] \cos( \theta) = \frac{base}{hypotenuse} \\ [/tex]
[tex] \cos( \theta) = \frac{13}{18} [/tex]
Now for finding the missing angle theta, inverse of cosine will be applied on the other side. Because, inverse of multiplication is division.
[tex] \theta = \cos {}^{ - 1} ( \frac{13}{18} ) [/tex]
[tex] \theta = \cos {}^{ - 1} (0.7222222222) [/tex]
[tex] \boxed{ \theta \approx \: 43.76174269 \degree}[/tex]
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