1. A COMPUTER FOR SOLVING TRIANGLES, COMPRISING A FLAT SHEET-LIKE BASAL PLATE HAVING AN ARCUATE GRADUATED SCALE OF AT LEAST 90* THEREON DESCRIBED ABOUT A CENTER ON SAID BASAL PLATE, SAID BASAL PLATE HAVING STRAIGHT HORIZONTAL AND VERTICAL SIDE EDGES AN X-LINE WITH AN X-SCALE EXTENDING ACROSS THE SAME PASSING THROUGH SAID CENTER AT ITS ZERO READING AND GRADUATE TO READ FROM LEFT TO RIGHT AND PROVIDING A STRAIGHT EDGE MARGIN, PARALLEL WITH THE BOTTOM EDGE OF SAID PLATE, MOVABLE ARM MEANS SOLELY PIVOTALLY FIXED TO SAID BASAL PLATE AT SAID CENTER AND HAVING A FREE END PART EXTENDING ACROSS SAID ARCUATE SCALE, SAID ARM MEANS INCLUDING A LONGITUDINALLY EXTENDING GRADUATE SCALE, A RIDER HAVING A FOOT COMPRISING A FOLDED-OVER PART IN THE FORM OF A GUIDE CHANNEL ENGAGING AGAINST AND OVER SAID BOTTOM EDGE OF SAID BASAL PLATE WITH AIR SPACE BEBETWEEN SAID FOLDED-OVER PART AND SAID PLATE, SAID FOLDEDOVER PART PROVIDING LONGITUDINAL GUIDING ENGAGEMENT WITH SAID BOTTOM EDGE OF SAID BASAL PLATE, AND PROVIDING MANU-