Let cos31 ° = α, then sin39 ° + tan149 °=

sin31°=√(1-cos²31°)=√(1-a²)
Original formula = sin (60 ° - 31 °) + sin (180 ° - 31 °) / cos (180 ° - 31 °)
=sin60°cos31°-cos60°sin31°-sin31°/cos31°
=√3/2cos31°-sin31°/2-sin31°/cos31°
=√3/2*a-√(1-a²)/2-√(1-a²)/a

RELATED INFORMATIONS

1. If cos 31 ° is known to be m, then sin 239 ° Tan 149 ° is given=______ (expressed by an equation with m)
2. What is the arc degree of the circle angle whose arc length is equal to radius? Such as the title
3. If the three sides of △ ABC are three consecutive positive integers, and a > b > C, 3b = 20acos & nbsp; a, then Sin & nbsp; a: Sin & nbsp; B: Sin & nbsp; C=______ ．
4. Mathematical simplification Evaluation M + 6 / m ^ 2-m-2 △ 3 / M + 2 times (1-1 / M + 2)
5. (3a-2b) ^ 2 - (3a + b) (3a-b) = (a-3b), known 9 ^ 2 = a ^ 4,4 ^ 2 + 2 ^ B, simplified evaluation There are two answers, quick Add (2a + b) at the end
6. If the result of (a + m) (a + 12) does not contain the linear term of a, then the value of M is () A. 2B. -2C. 12D. -12
7. How to calculate the multiplication and division method with letters? For example, 2 m times 2 m, 2 / 3 m times 3 m, 1 / 3 m divided by 2 m
8. Write out all the quartic monomials whose coefficients are half and contain the letters X and m without other letters I said one just now, but I didn't have three. I cheated my five points
9. If the quadratic equation MX ^ 2 + (2m-3) x + 4 = 0 has a positive root and a negative root, and the positive root is less than 1, the range of M is obtained
10. Known set M = {X5} n = {x | (x-3a) (x + 2a)
11. How many degrees is Tan 3 / 4?
12. Let a = 1 + tan10 / 1-tan10, B = tan10 + tan50 + √ 3tan10 * tan50, Find the size relation of a, B, a + B / 2, Is (a + b) / 2
13. The value of tan10 ° + tan50 ° + 3tan10 ° tan50 ° is () A. -3B. 3C. 3D. 33
14. If sina40 ° is known to be a, then cos130 ° is equal to a
15. If cos130 = a, tan50 If cos130 = a, tan50=
16. It is known that ∠ A is an acute angle, and if Sina = cos30 °, then Tana=
17. Find Sin & sup2; 1 ° + Sin & sup2; 2 ° + Sin & sup2; 3 ° sin²89°=?
18. It is proved that: (sin20 ° - √ (1-sin178; 20 °) / √ (1-2sin20 ° cos20 °) = - 1
19. What is the trigonometric function of sin 7 degrees 7 minutes 30 seconds?
20. Algebraic problems... Using the direct flattening method to solve equations Using direct flattening method to solve equation (1)2(x+a)^2÷3=8 (2)2(4-x)^2÷3=6 Requirements process The first wrong number should be 4