Why is Tan ^ 2 [(B + C) / 2] = Tan ^ 2 (π - a) / 2 = cot ^ 2 (A / 2) in the acute triangle ABC

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• 1. In the triangle ABC, M is the midpoint of B and C. The three (1) of the triangle AMC determine the shape of the triangle (2) find that the COSA edge is three consecutive integers and Tanc = cotb In the triangle ABC, M is the midpoint of B and C, and the three sides of AMC are three consecutive integers and Tanc = cotbam. 1) judge the shape of the triangle. (2) find out that the COSA side is three consecutive integers and Tanc = cot
• 2. In △ ABC, ∠ a + ∠ C = ∠ B, then △ ABC is______ A triangle
• 3. Sin equals to contrast, cos equals to neighbor and Tan cot. how can I remember them well? I always forget them
• 4. Sin = contrast skew cos = neighborhood skew Tan = contrast skew can only be used in right triangles or all triangles
• 5. Knowledge of triangles In the triangle ABC, BC = a, AC = B, ab = C. if the triangle ABC is not a right triangle, but an acute triangle or an obtuse triangle, please analogy Pythagorean theorem, try to guess the relationship between the sum of squares of a and B and the square of C, and explain the reason
• 6. If the distance from point P to the right focus on the hyperbola x213-y212 = 1 is equal to 13, then the distance from point P to the right collimator is () A. 135B. 13C. 5D. 513
• 7. Given that the distance from a point P on the hyperbola X & # 178 / 36-y & # 178 / 64 = 1 to a focus of the hyperbola is equal to 9, find the perimeter of △ pf1f2
• 8. Given Tan α = 2, find the value of Sin & sup2; α + 2Sin α cos α + 2?
• 9. If Tan α = 4, then 2Sin α & sup2; + sin α cos α + 3 =?
• 10. It is known that 2sin2 α + 2Sin α cos α 1 + Tan α = K (0 ＜ α＜ π 2)
• 11. Mathematical triangle knowledge There is an angle of 30 ° in a right triangle. What's the relationship between the three sides
• 12. Basic knowledge of triangle The school has a piece of green space. First, I plan to start from the position indicated by point d (BD: DC = 2:1). I hope the green space on both sides of the small ditch is equal. Now D is not the midpoint of BC. How can I divide the green space into two equal blocks and pass through point d?
• 13. Simplifying a & sup2; SIN3 / π + B & sup2; Cos π / 6-absin π / 4cos π / 4tan π / 3 + abcos π / 6 = process
• 14. It is known that the angle α is an acute angle
• 15. Let α be an acute angle and prove: sin α + cos α
• 16. It is known that θ is a positive acute angle, and sin θ + cos θ is proved Sin θ + cos θ = sin (θ + 45 °) twice the root sign
• 17. It is known that α is an acute angle
• 18. It is proved that: (1-sin2 α) / (Cos2 α) = (1-tan α) / (1 + Tan α)
• 19. Given Tan α = 1 / 2, find Sin & # 178; α - cos & # 178; α=
• 20. If sin (a + b) = 1, then Tan (2a + b) + tanb