As shown in the figure, the quadrilateral ABCD is a parallelogram, ∠ ADC = 125 ° and ∠ CAD = 21 ° to calculate the degree of ∠ ABC and ∠ cab

As shown in the figure, the quadrilateral ABCD is a parallelogram, ∠ ADC = 125 ° and ∠ CAD = 21 ° to calculate the degree of ∠ ABC and ∠ cab

As shown in the figure, ∵ quadrilateral ABCD is a parallelogram, ∵ ADC = 125 °, ∥ ab ∥ CD, ∵ ABC = ∥ ADC = 125 °, ∵ ADC + ∥ DAB = 180 °, then ∵ DAB = 180 ° - 125 ° = 55 °. And ∵ CAD = 21 °, ∵ cab = ∵ DAB - ∥ CAD = 55 ° - 21 ° = 34 °

It is known that a and B are the moving points on the unit circle O, and a and B are in the first and second quadrants respectively, C is the intersection of the circle O and the positive half axis of X axis, and △ AOB is an isosceles right triangle, with ∠ AOC = α. (1) find the coordinates of point a as (35, 45), and find the value of sin2 α + sin2 α Cos2 α + Cos2 α; (2) find the value range of | BC |

(1) It is known that: Tan α = YX = 4535 = 43, (2 points) then sin2 α + sin2 α Cos2 α + Cos2 α = sin2 α + 2Sin α cos α Cos2 α & nbsp;; + Cos2 α - sin2 α (4 points) = tan2 α + 2tan α 2-tan2 α (6 points) = (43) 2 + 2 × 432 - (43) 2 = 20; (2) according to the meaning of the question: a = (cos

It is known that a is the point on the unit circle, and point a is in the second quadrant, and point B is the intersection of this circle and the positive half axis of X axis. Let ∠ AOB = a, if the ordinate of point a is 3 / 5,
Then Sina =? Tan2a =?

Analysis:
From the definition of trigonometric function of any angle and the knowledge of sine of unit circle, we can get that sina = 3 / 5
Since the end of angle a is in the second quadrant, there is cosa