8. B 令40° -α=β ,则 10°+2α=90°-2β ,即 cos β=3/5,sin(10°+2α)=sin(90 ° 2β)=cos2β=2cos^2β-1=2*(3/5)^2-1=-7/(25) .B. 9.C 由 (OA)⋅(OB)=0 易知直线AB过定点(4,0),可设AB的方程为x=ky+4, 取力方程 \(x-ky+4.yy^2-4x.. 消去...
解:(1)sin54°+sin66°=2sincos=2sin60°cos6°=sin6°;(2)cos40°+cos52°=2coscos=2cos46°cos6°;(3)sin3x-sin5x=2cossin=2cos4xsin(-x)=-2sinxcos4x;(4)cos50°-cos70°=-2sinsin=-2sin60°sin(-10°)=2sin10°sin60°=sin10°. 利用三角函数的和差化积公式,诱导公式即可...
③“a=1”是“函数y=cos2ax的最小正周期为π”的充分不必要条件④直线x-2y+5=0与圆x2+y2=8交于A、B两点,则 |AB|=2 2⑤若直线2ax-bx+8=0(a>0,b>0)平分圆x2+y2+4x-8y+1=0周长则 8 a+ 2 b最小值为9. 给出以下四个命题:①过点(-1,2)且在x轴和y轴上的截距相等的直线方程是x...
sin4x-cos4x=(sin2x+cos2x)(sin2x-cos2x)=-cos2x.故答案为:1+sin2x;14sin4x14sin4x;-cos2x.(2)1sin10°1sin10°-√3cos10°3cos10°=cos10°−√3sin10°sin10°cos10°cos10°−3sin10°sin10°cos10°=−2(√32sin10°−12cos10°)sin10°cos10°−2(32sin10°−12cos10°...
若圆x2+y2-4x-2y+c=0与y轴相交于A、B两点,圆心为P,若∠APB=90°,则c的值为( ) A、8 B、3 C、-3 D、- 1 3对具有线性相关关系的变量x和y,测得一组数据如下表 x 2 4 5 6 8 y 30 40 60 50 70若已求得它们回归方程的斜率为6.5,则回归方程为( ) A、y=6.5x+17.5 B、y=6.5x+8.7...
三、 填空题:本大题共4小题,每小题5分,共20分13.计算(2cos20°-cos40°)/(sin40°)=14.已知数列 \(a_n\) 满足:对任意的正整数m,n,都有 a_ma_n=a_(m+n) ,且 a_2=3,4 a1=15.已知抛物线 C_1:y^2=4x ,圆 C_2:(x-2)^2+y^2=2 ,直线 l:y=k(x-1) 与C交于A,B两点...
三、解答题(本大题共4小题,共40分)11.(10分)化简下列各式:11(1)tan 0 1+tan 02cos4x-2cos2x+2(2)2tan(π/4-x)sin^
Answer to: Evaluate the integral. \\ \int \sin(4x)(\cos(4x))^{(\frac{1}{3})} By signing up, you'll get thousands of step-by-step solutions to your...
两边同时除以cos\theta: 2 sin\theta =(1-2sin^2\theta) - 2sin\theta sin\theta = 1 - 4sin^2\theta 也就是: 4sin^2\theta + 2sin\theta - 1 = 0 令x = sin\theta,我们就得到了一个一元二次方程: 4x^2 + 2x - 1 = 0
Proving trigonometric function is a method the same as solving an equation that the equation will be proving to make both the sides of the equation are true or equal. Answer and Explanation: Given that sin(4x)=cos(x)(4sin(x)−8sin3(x)). Let us consider the......