# Cosine + real numbers - problems

1. Trigonometric functions
In right triangle is: ? Determine the value of s and c: ? ?
2. Regular 5-gon
Calculate area of the regular pentagon with side 7 cm.
3. Forces
In point O acts three orthogonal forces: F1 = 20 N, F2 = 7 N and F3 = 19 N. Determine the resultant of F and the angles between F and forces F1, F2 and F3.
4. IS triangle
Calculate interior angles of the isosceles triangle with base 38 cm and legs 26 cm long.
5. Cuboid
Determine the dimensions of cuboid a, b, c; if diagonal d=9 dm has angle with edge a α=55° and has angle with edge b β=58°
6. Triangle TBC
TBC is isosceles triangle with base TB with base angle 63° and legs length |TC| = |BC| = 25. How long is the base TB?
7. Cotangent
If the angle α is acute, and cotg α = 1/3. Determine the value of sin α, cos α, tg α.

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