一、对于给角求值问题,运用口诀求解求kπ/2±α,k∈Z的三角函数值,考生可记住口2诀:奇变偶不变,符号看象限.奇变偶不变是指当k为奇数时,正弦(切)变余弦(切),余弦(切)变正弦(切);当k为偶数时,函数名不变.符号看象限是指在α的三角函数值的前面加上符号,即当α为锐角时,原来的角所在象限对应的函数值的符号. First, for the problem of angular evaluation, the use of formulas to find the trigonometric function to find kπ / 2 ± α, k∈Z, candidates can remember the mouth 2 tactics: Odd even unchanged, the symbol to see the quadrant. Odd even unchanged Refers to the sine (cut) variable cosine (cut), cosine (cut) sinusoidal (cut) when k is an odd number; the function name is constant when k is even number symbol quadrant refers to the trigonometric function value The sign is added to the front, that is, the sign of the function value corresponding to the quadrant where the original angle is located when α is an acute angle.