PA, Pb and PC are three rays from P, and the angle between each two rays is 60 degrees. So what is the cosine of the angle between PC and PAB? Which is the angle between PC and PAB and why A proof of the angle between line PC and plane PAB

This is a regular triangle with all angles of 60 degrees. Set the edge length to 2, and the height of the triangle is the root sign 3. The sine and cosine of the angle in the question are 2 / 2 root sign 3
Set a midpoint on the side of AB as D, then the angle cpd is the angle required in the title

PA, Pb and PC are three rays from P, and the angle between each two rays is 30 degrees. Then the cosine of the angle between PC and PAB is 0

In this paper, the length of PC pH (H point is the perpendicular foot from C point to AB in the triangle ABC) ch is calculated as PC = 1 / sin (15), pH = Tan (75) HC = Tan (60)

RELATED INFORMATIONS

1. We know that the line AB = 8, and there is a point P on the plane. (1) if AP = 5, what is Pb equal to, P is on the line AB?
2. PA, Pb and PC are three rays starting from point P. the angle between each two rays is 60 degrees. Then the cosine of the angle between PC and PAB is () A. 12B. 22C. 33D. 63
3. Point P is on the vertical bisector of line AB, PA = 7, then Pb=______ ．
4. Know a (2,1), B (1,3), find a point P on the x-axis, so that the value of PA + Pb is the minimum, then what is the minimum value?
5. Given the straight line L: 2x-y + 1 = 0 and the point a (- 1,2) B (0,3), try to find a point P on L, so that the value of PA = Pb is minimum, and find the minimum value
6. Given the points a (- 2,5) and B (2,4), find a point P on the straight line L: 2x-2y + 1 = 0, so that | PA | + | Pb |, and find the minimum value
7. Given the points a (- 1,0), B (1,0), P is the moving point on the line 2x-y + 1 = 0. (1) when the vector PA * and the vector Pb take the minimum value, we find the coordinates of the op vector and Co And find the value of COS angle APB (2) if P satisfies PA + Pb = pa-pb, the coordinates of P
8. It is known that two points a (- 5,2) and B (- 1,7) in the rectangular coordinate plane can find point P on the coordinate axis, so that point PA = Pb
9. Given that the two points in the Cartesian coordinate plane are a (2,2), B (- 1, - 2), P is on the X axis, and PA = Pb, the coordinates of point P are obtained
10. Point Q moves on the curve X ^ 2 + y ^ 2 = 1, and the symmetric point of point Q about point a (1, - 1) is p. find the trajectory equation of P
11. If PA = 8, Pb = 5 and OA: OB = 4: √ 3, then the distance from point P to plane a is equal to
12. As shown in the figure, PA ⊸ o is in the plane, AB is the diameter of ⊙ o, C is the point on ⊙ o, and E.F is the point a in the plane PB.PC The following conclusions are given: 1, AF ⊥ Pb; 2, EF ⊥ Pb; 3, AF ⊥ BC; 4, AE ⊥ plane PBC, where the sequence number of the correct proposition is
13. P is a point out of plane a. the angle difference between PA, Pb and plane a is π / 4. Their projective lengths in plane are 2 and 12 respectively. The distance from P to plane is
14. Why are the same chords complementary to each other? How to prove the complementarity or equality of the circle angles of the same chord?
15. If a chord of a circle is known to divide the circle into two parts of 1:3, then the degree of the angle of the circle to which the chord is directed is______ ．
16. A chord is divided into two parts: 1:4. Find the degree of the circumference angle of the chord
17. If the distance from the center O to the chord AB is a, then the diameter of O is a
18. Given the set a = {x | - 5 ≤ x ≤ 3}, B = {y | = a-2x-x & sup2;}, where a ∈ R, if a is contained in B, find the range value of real number a RT
19. We know that set a = {x 3} and set B = {x 4x + M
20. Given the set a = {a, a + D, a + 2D}, B = {a, AQ, AQ & sup2;}, (a is a known constant), if a = B, find the value of D, Q